The Big Bang Theory (season 6)

At the International Space Station, Howard receives a call from his mother, who is furious at him on finding out that he is planning to move out and live with Bernadette after he returns from space. Not wanting to disappoint his mother, who wants him to stay, and Bernadette, who wants him to move out, he lies to both of them.

Meanwhile, Raj, who is feeling lonely now that Howard is in space, is invited by Sheldon to his second anniversary date with Amy on the pretext of "outsourcing" any romantic activities he must perform with Amy as stipulated in the Relationship Agreement to an Indian. Amy is not happy with Raj's presence and forces him to leave. After this, he goes over to Leonard and Sheldon's apartment, where Leonard and Penny are spending the evening together to talk about the status of their relationship. Leonard is unhappy with Raj's intrusion, but is forced to accommodate him because of Penny, who is unwilling to talk about their relationship. When a drunk Raj starts forcing Penny to declare her love for Leonard, he is thrown out of the apartment. He then goes over to the comic book store, where he and Stuart bond over a nightcap following which they decide to hang out together the following night.

Elsewhere, Sheldon and Amy's date is not going too well. Sheldon is unable to comprehend Amy's flirtatious gestures, prompting the latter to walk out of their date in disgust. When he demands that she come back because he needs her to drive him home, she returns and tells him to say something romantic to her from his heart, failing which she will break up with him. Sheldon then offers a stunningly romantic soliloquy, which she finds incredibly touching until she finds out that it is a quote from the first Spiderman movie.

Recurring characters: Kevin Sussman as Stuart Bloom, Carol Ann Susi as Mrs. Wolowitz and Pasha Lychnikoff as Dimitri Rezinov
Note: The title sequence was updated with this episode to include Mayim Bialik and Melissa Rauch in the last image of the sequence.
Note: Mark Cendrowski was nominated for the Directors Guild of America Award for Outstanding Directing – Comedy Series for this episode.

While sorting out Bernadette's wedding gifts, Penny confesses that she is unsure of her feelings towards Leonard and where their relationship is going, and is worried she might break up with him again. She asks Bernadette and Amy not to mention this to Leonard; however, Amy tells it to Sheldon. He is unable to keep the secret, but restrains himself from spilling the beans to Leonard. Later that night, he enters Penny's apartment, wakes her up and tells her not to break up with Leonard regardless of her feelings towards him. The next day, Penny decides to talk to Leonard about her fears and doubts, but just as she is about to do so, she looks at Leonard's sad face and ends up sleeping with him instead. Later, she insists she's fine with where they are going, as they aren't getting married.

Meanwhile, Stuart joins the gang, subject to Sheldon's condition that he acts like Howard, who he is replacing as Raj's friend. This includes having Raisinets while watching a movie and playing the same cards Howard plays during Mystic Warlords of Ka'a. Later he and Raj go to a bar meet some women, which is reminiscent of the old Howard and Raj friendship.

Elsewhere, at the space station, Howard is being bullied by his co-astronauts Mike Massimino and Dimitri Rezinov. When Bernadette finds out, she tells him to stand up to them. He does so, but ends up having a mouse face along with his nickname Froot Loops drawn on his face by the duo.

Recurring characters: Kevin Sussman as Stuart Bloom, Pasha Lychnikoff as Dimitri Rezinov and Mike Massimino as himself

Sheldon receives his childhood scientific journals from back home in the hope of getting a Nobel Prize for any extraordinary research he may have done in his childhood. He feels too important to read the journals himself, so he hires an attractive female grad student Alex Jensen to do the work. She surprisingly tolerates Sheldon and his eccentricities, having been brought up in a family of scientists. When Amy finds out about Alex, she becomes jealous and investigates Sheldon's office, despite Penny's assurances that Alex is not interested in Sheldon. Later, in the Caltech cafeteria, Amy and Penny notice Alex and Leonard talking with each other, with Alex actually flirting with him making Penny jealous. Amy then points out that even though Penny has said she is still unsure of her feelings for Leonard, subconsciously the thought of him with another woman definitely bothers her, and Penny slowly realizes that Amy may be right. That night, Alex comes over to Leonard and Sheldon's apartment after finding out that one of Sheldon's elementary school projects actually qualifies for a Nobel Prize and flirts with Leonard again, prompting Penny to immediately take him to her apartment for sex.

Meanwhile, Howard is homesick and wants to return to the Earth as soon as possible. When the Soyuz capsule to take him and his co-astronauts home is delayed, he finally cracks and starts suffering anxiety attacks and blabbering nonsense. Eventually, the other astronauts give him a sedative which makes him relax, but also causes him to act strangely, such as taking off his pants and windmilling in the space station.

Recurring characters: Pasha Lychnikoff as Dimitri Rezinov and Margo Harshman as Alex Jensen

After losing badly to Penny and Amy in Pictionary, Sheldon and Leonard challenge them to a series of games after Penny declares that she can beat them at anything.

Meanwhile, Howard returns to the Earth and is expecting a grand welcome from the public and his friends. Only Bernadette receives him at the airport, with the grand welcome from the public reserved for Howie Mandel. The couple then go to Bernadette's apartment to enjoy their "honeymoon", which is cut short as Bernadette, who is having the common cold, falls asleep immediately after taking Benadryl. Howard leaves for his home, where he is shocked to find out that his mother is having an affair with his dentist. He then goes to Raj's apartment, where he finds out that Stuart, who is now staying with Raj, has replaced him as Raj's best friend; they had even planned to go to a Sound of Music sing-along. He immediately leaves for Leonard and Sheldon's apartment, but leaves as soon as he arrives after Leonard, Sheldon, Penny and Amy, who are still engaged in their contest, shoo him away. Finally he ends up in a diner, where he realizes that he has caught Bernadette's cold.

Recurring characters: Carol Ann Susi as Mrs. Wolowitz, Pasha Lychnikoff as Dimitri Rezinov and Mike Massimino as himself
Guest stars: Jan Hoag as Lilian, Ken Lerner as Dr. Schneider, and Howie Mandel as himself
Note: Kevin Sussman became part of the main cast with this episode.

Stuart decides to organize a Halloween costume party at the comic book store, with Raj being the party manager. While Amy and Bernadette decide to go with Sheldon and Howard respectively, Penny is not interested as she does not like going to parties at the comic book store. Amy and Bernadette then convince her to show interest in Leonard's activities just as how Leonard shows interest in her activities even though he actually does not like them. Listening to their advice, she visits Leonard's lab the next day, where she is really fascinated by his work, as a result of which she gets turned on and ends up having sex with him in the lab. This repeats every time she visits Leonard's lab or whenever Leonard shows how smart he is. At the party too, they end up having sex in a similar fashion.

Meanwhile, Sheldon and Amy argue over what couple they should go as to the party. While Amy suggests Romeo and Juliet or Raggedy Ann and Andy, Sheldon prefers R2-D2 and C-3PO, Hewlett and Packard or salt and pepper. Eventually both agree to a compromise- Amy dresses up as Raggedy Ann, while Sheldon dresses up as Raggedy C-3PO.

Elsewhere, Howard cannot stop talking about his space mission, which bores his friends and even Bernadette. Before having sex, Bernadette tells him that she and the others are tired of listening to his adventures his space and forbids him from talking about it, which does not go down well with him. He refuses to attend the party unless he can talk about his space mission, but is eventually forced to attend by Bernadette. At the party, he lashes out at Raj for forcing him to keep quiet about his space mission, following which Bernadette confronts him, upon which he reveals that without his space adventure, he is "just Howard Wolowitz". Bernadette then consoles him, saying that she fell in love with "just Howard Wolowitz", after which they kiss. Later that night, Raj sends Howard a video of astronaut Buzz Aldrin irritating children by constantly referring to his trip to the Moon. On seeing the video, Howard finally realizes how irritating his constant mentioning of his space mission sounded to others.

Guest stars: Buzz Aldrin as himself and Janelle Marra as Claire

Penny rejoins community college in a bid to clear history so that she can finally graduate. She does not want Leonard to know as he would get very excited about it, but on Bernadette's and Amy's advice, she tells him anyway. Later that night, Leonard reads Penny's homework paper on slavery, which turns out to be really bad, so he rewrites it entirely and shows it to Penny the following morning, but she lashes out at him and refuses to accept the paper, adding that she will do all her college work without anyone's help. Later, Penny shows Leonard that she had got a B- in her paper without taking anyone's help and mocks him for not thinking that she was smart enough. It then turns out that Bernadette and Amy had helped her in rewriting the paper.

Meanwhile, Sheldon starts playing the online game Words with Friends with Stephen Hawking and manages to win almost every game against him. Hawking eventually stops playing, which makes him distraught, thinking that Hawking stopped playing with him because he was beating him continuously. The next day, Hawking again starts playing with Sheldon, who in a bid to ensure that Hawking does not stop playing with him again, purposely loses to him. That night, he receives a phone call from Hawking, who mocks him for losing. The episode ends with Hawking asking "What do Sheldon and a black hole have in common?" and leaving Sheldon guessing. Hawking tells him, "they both suck".

Guest star: Stephen Hawking as himself (voice)

Sheldon invites Wil Wheaton for a special Fun With Flags podcast about Star Trek flags. Wheaton and Amy do not get along, prompting Amy to request Sheldon to ask Wheaton to leave. When he refuses, she leaves in a huff, creating a standoff between the two. After unsuccessfully trying to make Amy respect Wheaton, he confesses his relationship worries to Penny at the Cheesecake Factory bar, who chides him for not standing up for Amy when Wheaton was insulting her despite being a Texan. In the course of their conversation, he also gets drunk after Penny mischievously offers him Long Island Iced Tea. Still drunk, he then goes over to Wheaton's house and forces him to apologize to Amy, challenging him Texan style. Wheaton, who is surprised by Sheldon's drunk behavior, does apologize, shortly before Sheldon comes to his senses and vomits in his shrubs. Later, Sheldon and Amy, who have now reconciled, reshoot the special podcast with LeVar Burton as the special guest, but Amy does not get along with him either.

Meanwhile, Howard finally moves into Bernadette's apartment after Bernadette reminds him of his promise to her that he would move out of his house once he returns from space. While unpacking his things at Bernadette's apartment, he comes across his old magic set. He then reminisces about how he used to cheer up his mother by performing magic tricks after his father left them. On hearing this, Bernadette changes her mind and forces him to move back in with his mother, at least until he does not have mother issues.

Recurring characters: Wil Wheaton as himself and Carol Ann Susi as Mrs. Wolowitz
Guest star: LeVar Burton as himself
Note: Jim Parsons won the Primetime Emmy Award for Outstanding Lead Actor in a Comedy Series at the 65th Primetime Emmy Awards for this episode.

Leonard becomes jealous of Penny's classmate, a British student named Cole, who is working with Penny on an oral class project, thinking that he is probably hitting on her. When he encounters Cole in the apartment lobby, he indirectly threatens him to stay away from Penny, oblivious to the fact that Cole is not interested in Penny. Unfortunately for him, Penny notices this and becomes infuriated at him, upset at the fact that he is not trusting her. The next day at the Caltech cafeteria, Leonard talks about his problem with Alex, who starts flirting with him in reply, though he is unaware that she is hitting on him. That night, he meets Penny in the lobby and after revealing to her that he is really insecure about other men hitting on her, she confesses her love for him, which shocks both of them as it is the first time ever that Penny confessed her true feelings for Leonard. They awkwardly decide to pretend it's not a big deal.

Meanwhile, Howard and Raj wonder where Sheldon disappears between 2:45 pm to 3:05 pm every day. They follow him down to Caltech's basement and notice him entering a storage room. They return to the basement at midnight and break into the room, only to find a chalkboard with the number "43" written on it. After breaking their heads over-thinking what the "43" actually means, Howard installs a camera which he stole from the Mars Rover so that they can spy on what Sheldon does in the room. Unfortunately, Sheldon finds out that Howard and Raj are spying on him using the camera and creates a phony video of himself being attacked by an alien creature in the room after creating a small wormhole to find life in the 44th parallel universe (with the previous "43" universes having no life). He then confronts the duo, admonishes them for spying on him and reveals that he goes into the room to relax his mind from the difficulties he has to face in his daily life, but refuses to tell them what the "43" means. It is then revealed to the audience that Sheldon plays with a hacky sack in the room, with the "43" on the chalkboard being the maximum number of consecutive hacky sack hits that he has achieved.

Recurring character: Margo Harshman as Alex Jensen
Guest star: Ryan Cartwright as Cole

Using the money he earned from the space mission, Howard buys a new car. He is also assigned Sheldon's parking space, as Sheldon has never used it. This does not go well with Sheldon, who wants his parking space back even though he does not own a car and does not know how to drive, and begins to engage in a bitter feud with Howard to get back his parking space. Sheldon takes Howard's Iron Man helmet and sits in Howard's car naked, after Howard sits in Sheldon's spot naked. The fight eventually spills over to the girls' side too, with Amy and Bernadette supporting Sheldon and Howard respectively. Amy helps Sheldon deface the parking spot and parks her car there, and Bernadette responds by having it towed and scratching her car. Caught in the middle, Penny accidentally gets her nose broken by Amy when she tries to hit Bernadette. Raj finally ends their feud once and for all by making Sheldon and Howard foster an agreement where Howard keeps the parking space until Sheldon learns to drive or gets a Batmobile. Sheldon and Amy and Howard and Bernadette reconcile at The Cheesecake Factory, where a battered Penny approaches them and retorts "Yeah, everybody's happy. Great!" The episode ends with Sheldon taking his cushion to the dry cleaner's, as it was sat on by a naked Howard during their arguments.

Howard and Bernadette have dinner with Bernadette's parents. Howard, who doesn't get along with his father-in-law, is unable to start even a small and mundane conversation with him as they have nothing in common. Bernadette requests her father to take Howard fishing so that they can get a chance to know each other and bond together, an idea to which Howard and his father-in-law reluctantly agree. Since Howard does not know how to fish, nor do Leonard and Raj, he seeks Penny's help, as she is the only one in their gang who knows fishing. On the morning of the trip, Howard and his father-in-law both admit that their wives forced them to go fishing together. This admission actually makes them bond, as they finally found something they have in common: they have dominating wives, despite having successful careers. They decide to go to a casino in Palm Springs instead.

Meanwhile, Amy comes down with the flu. Sheldon reluctantly takes care of her, as it is mentioned in their Relationship Agreement that either partner has to take care of the other when he/she is sick. Amy enjoys being taken care of by Sheldon as it is the only time he shows his caring and loving side. Eventually she recovers, but she feigns her sickness so that he can continue to take care of her. The lie is exposed when Sheldon, who was concerned with Amy not recovering from her "illness" despite his best efforts, gets her cheek swab cultured in a lab, only to find out that she has recovered.

Recurring character: Casey Sander as Mike Rostenkowski
Guest star: Meagen Fay as Mrs. Rostenkowski
Note: Mayim Bialik submitted this episode for consideration due to her nomination for the Primetime Emmy Award for Outstanding Supporting Actress in a Comedy Series at the 65th Primetime Emmy Awards.

The guys and Stuart decide to play Dungeons and Dragons on Saturday night and forbid the women from participating. Leonard, who is the dungeon master, sets up a Christmas theme for the game where Santa Claus must be rescued from a gang of ogres, much to Sheldon's chagrin, who doesn't like Christmas. As the game progresses, Raj's character is killed, prompting him to leave the game and join Penny, Bernadette and Amy on a girls' night out. They head to a bar, where the girls decide to find a woman for Raj. After being rejected by a woman who just broke up with her boyfriend, Raj laments about how he is unable to get a girlfriend despite being successful. The girls sympathize with him, with Amy even sharing her experiences of loneliness with him. This makes him happier, though it also makes him attracted to Amy, the only woman in their gang he was not attracted to so far.

Meanwhile, back at Leonard and Sheldon's apartment, the guys' game continues. When they reach the dungeon where Santa is imprisoned, Sheldon paralyzes Howard's and Stuart's characters and yells at Santa for not bringing back Pop-Pop (Sheldon's late maternal grandfather, the only member of Sheldon's family who encouraged his scientific pursuits) from the dead, which is what he'd asked for when he was a child. He refuses to help Santa, who is then eaten alive by the ogres. Later, Sheldon has a nightmare in which he finds Santa in the living room; Santa says he is sorry for being unable to bring someone back to life, and says he has a present for Sheldon; anticipating a train, Sheldon is horrified to see Santa firing a cannon at him, and wakes in a panic.

Guest star: Dakin Matthews as Santa

Alex is planning to attend Kip Thorne's lecture about quantum foam on Saturday and invites Leonard to accompany her. Though he declines as he has a date with Penny the same day, Alex offers to talk about the lecture "over dinner". Leonard realizes that Alex is hitting on him, and he is stunned over being the object of attention from two beautiful women (more stunned that it's two at the same time), which flatters him, though he is still committed to his relationship with Penny. When Sheldon finds out, he gets frustrated at Alex as he feels that she needs to solely dedicate her time to him since she is his assistant. On Bernadette's advice, Sheldon talks to Alex the next day about the issue. He inadvertently uses sexually inappropriate language while talking to her, prompting her to file a sexual harassment complaint against him with the HR Department. At the HR Administrator's office, Sheldon insults the female HR admin by inadvertently blurting out racist (the HR admin is African American) and misogynist comments, which makes her furious, but then he lodges complaints on Leonard, Howard and Raj for some earlier misdemeanours in an attempt to draw the admin's anger away from him. Meanwhile, Leonard plays his cello to apologize to Penny, and tries to convince her that he doesn't have feelings for Alex, but she still feels insecure. He assures Penny that she is the only one for him, just before he, Howard and Raj are called to the HR admin's office as well. The admin eventually instructs Sheldon to take an online seminar on sexual harassment; Sheldon forces Alex to complete it, not wanting to waste time on such "nonsense". Later, Penny tells Leonard that she has found a way to deal with her insecurities: she dons a pair of thick-rimmed glasses to look like a scientist, which turns Leonard on like crazy.

Recurring characters: Regina King as Janine Davis and Margo Harshman as Alex Jensen

The guys decide to go to the Bakersfield Comic-Con. On the way, they make an unscheduled stop at Vasquez Rocks, where the original Star Trek: The Original Series was filmed. There they dress up as Star Trek: The Next Generation characters, but whilst they are taking pictures of themselves someone steals Leonard's car. Stranded in the middle of the Californian desert, unable to change back into their regular clothes and with no other means of transportation or communication (the guys' clothes and phones were in the car), the four try to hitch a ride to Bakersfield, but no one stops for them. They then walk to a nearby diner, where they lodge a complaint about Leonard's stolen car with a police officer. Demoralized, the four skip Comic-Con and return to Pasadena in a rental car arranged by Howard's mother.

Meanwhile, the girls wonder how the men are into comics and superheroes, stuff which they believe are only for kids. To find out, they go to the comic book store and buy some comic books. When they return to Penny's apartment, they read them and then find themselves drawn into a heated argument about Thor's hammer Mjolnir. They even enter Leonard and Sheldon's apartment and read their comics to prove their points about Thor and his hammer.

Guest stars: Matt Battaglia as Officer Reynolds
Note: This episode was the series' first to garner 20 million viewers,^[6] and was the most watched episode of season 6.

Howard and Raj order customized action figures of themselves. The figures they actually receive do not look like them. They then buy a 3D printer for $5000, which they use to make precise figures of themselves and Bernadette. When Bernadette sees the figures of Howard and herself, she is very happy until she finds out how much Howard paid for the printer. She removes Howard from their joint account until he realizes the value of money. The next day, he sells his half of the printer to Raj.

Meanwhile, Sheldon and Kripke are forced to work together on a fusion reactor project. To Sheldon's dismay, Kripke's work turns out to be far superior and more advanced than his. This makes him so upset that he even allows Amy to hug him. The next day, Kripke confronts him over the poor quality of his research, but thinks that it is because he now has a girlfriend with whom he has constant sex. Surprisingly, Sheldon does not object to Kripke's incorrect theory and goes along with that story so that Kripke and his other colleagues never realize that he is not the smartest person in Caltech. In conversation with Penny that evening, he tells something completely unbelievable which shocks Penny: he reveals that it is a "possibility" that he could one day have a physical relationship with Amy.

Recurring character: John Ross Bowie as Barry Kripke

After Sheldon gives away the ending of Harry Potter and the Half Blood Prince which Leonard is reading, Leonard gets into a heated argument with him, following which he decides to leave their apartment and move in with Penny. Penny is uncomfortable with her boyfriend moving in with her, though she is unable to convince him to move back with Sheldon. Meanwhile, Amy decides to move in with Sheldon after finding out that Leonard moved out, which Sheldon finds uncomfortable. Later, Sheldon and Penny comfort each other over their similar predicaments and decide to tell the truths to their respective partners. When Sheldon tells Amy to move out, she gets incensed at him. He gets scared and tells her that the reason he does not want her to live with him is that Leonard may come back since Penny does not want to live with him. This causes a brief spat among the quartet. Amy eventually gets so angry at Sheldon and Leonard that she decides to move in with Penny, a suggestion which makes Penny uncomfortable again. A dejected Leonard then moves back in with Sheldon, but not before Sheldon gives away the plot of a The Walking Dead episode.

Meanwhile, Howard asks Raj to visit his mother, who is depressed ever since she broke up with her dentist boyfriend, while he is away on a trip with Bernadette and her colleagues to Las Vegas. At the Wolowitz residence, Raj sees how depressed Mrs. Wolowitz is, prompting him to spend the night there. She begins to pamper him just like she used to pamper Howard and prevents him from leaving, hiding his clothes and car keys. Eventually, he tries to escape from Howard's bedroom window, but is pulled back by Mrs. Wolowitz.

Recurring character: Carol Ann Susi as Mrs. Wolowitz
Note: This is the first episode in which Mrs. Wolowitz is clearly shown on the screen, confirming her obesity. Her face is not shown. The identity of the actress playing her part is unknown. She had previously appeared only briefly, sitting on the rooftop at the wedding in the season 5 finale "The Countdown Reflection".

On Valentine's Day, Leonard and Penny go on a double dinner date with Howard and Bernadette to a fancy restaurant. Howard and Bernadette are in a foul mood and constantly bicker during the date, due to Bernadette taking away Howard's Xbox when he was caught playing Assassin's Creed instead of doing the laundry. Leonard and Penny, on the other hand, are quite happy until Penny sees her ex-boyfriend proposing to his girlfriend. She becomes extremely uncomfortable and starts obsessing about them, which upsets Leonard, causing a fight between the couple. When they return home later that night, Leonard confronts Penny for ruining their Valentine's Day, to which Penny finally reveals her fears; if their relationship continues to be steady, Leonard would propose marriage to her, which she is still not ready for. At this, Leonard suggests that she proposes to him whenever she is ready to get married; he will not propose to her ever again. Penny then asks Leonard to be her valentine, which he accepts.

Meanwhile, Sheldon plans to buy the best Valentine's Day gift for Amy. He entrusts this work to Alex, who buys three for him to choose from: a music box shaped like a harp which plays Amy's favorite songs, a map of England showing the journeys of the characters from The Canterbury Tales and a rare signed print of Santiago Ramon y Cajal's drawings of brain cells. He picks the latter, but decides to keep it for himself. Later that night, Amy comes over and suggests that they celebrate in a manner he would enjoy - no romance or gifts, order a pizza and watch either a Star Trek or a Star Wars movie. Sheldon is impressed with Amy's gesture and in return makes her his emergency contact; initially delighted, she quickly becomes exasperated when she has to keep leaving work to attend to the imaginary illnesses caused by his hypochondria.

Elsewhere, Raj and Stuart, both of who do not have a date for Valentine's Day, throw a party at the comic book store on Valentine's Day for those people who do not have dates for the occasion. During the party, Raj speaks about how single people are not truly alone as long as they have each other, but when a young woman named Lucy starts talking to him and he asks her out for coffee, he derides the single people present at the party, including Stuart, and leaves the comic book store with her.

Recurring characters: Margo Harshman as Alex Jensen and Kate Micucci as Lucy
Guest stars: Josh Brener as Dale and Briana Cuoco as Gretchen

Following the previous episode, Raj and Lucy are having coffee. Lucy is clearly uncomfortable being with Raj and soon escapes from their date by pretending to go to the bathroom. This makes Raj extremely upset, as he feels that he is incapable of dating any woman, and shuts himself up in his apartment, refusing to go to work or hang out with his friends. When Howard confronts Lucy over her ditching Raj, she asks him to give Raj a note with her phone number. When Raj sees the note, he initially shows a lack of interest in resuming his relationship with Lucy, though he changes his mind eventually. Later, Lucy comes over to his apartment and apologizes to him for walking out of their date and when asked why, she reveals that she is very shy and uncomfortable around people she does not know, but she is working on it. At this, he becomes pleased and also reveals his selective mutism, which she does not believe, but accepts to go on another date with him to find out.

Meanwhile, Sheldon invites Penny as his special guest for a Fun With Flags podcast about the flag of Nebraska. Later, while chatting with Amy through webcam, Amy advises him to compliment Penny in return as she was helpful enough to star in his podcast. When he does so, she invites him to her class play A Streetcar Named Desire that Friday, which he reluctantly accepts to attend with Amy and Leonard on Amy's advice. The play turns out to be a success, with Penny putting up a strong performance, which impresses even Sheldon.

Recurring character: Kate Micucci as Lucy
Guest star: Riccardo LeBron as Tom

As part of their contract with Caltech, Leonard, Sheldon and Howard are required to serve on a committee that promotes science among young women. Neither Sheldon or Howard show any interest in this project, but on Leonard's cajoling, Sheldon suggests that they focus on middle school girls and inspire them to pursue science after they finish school. They go to Howard's old middle school to implement their ideas. At the school, they fail to enthuse the girls to show an interest in science. With their attempts to inculcate a love for science among the girls having failed, Sheldon contacts Amy and Bernadette to talk to the girls about pursuing a career in science as they are female scientists.

Meanwhile, the girls skip work and go to Disneyland. There, they head straight to a place where people are made to look like Disney princesses. All of them want to be Cinderella, but Bernadette insists that she be Cinderella since she planned the trip and drove them, forcing Penny to be Aurora from Sleeping Beauty and Amy to be Snow White. Back at their respective apartments, Bernadette's and Penny's costumes turn on Howard and Leonard respectively. On the other hand, Amy, still in her Snow White costume, wants Sheldon to kiss her Snow White-style, but he is not interested.

Elsewhere, Raj arranges a "texting date" with Lucy in the library, where they interact with each other by texting due to their social problems. At then end of their date, Lucy attempts to kiss Raj, but gets shy before doing so and leaves. This impresses Raj, who counts it as foreplay.

Recurring character: Kate Micucci as Lucy
Guest star: Brian Posehn as Bert

Sheldon is tricked into cleaning Howard and Bernadette's closet while at their dinner party. While doing so, he comes across a letter Howard's long-lost father had written to Howard on his 18th birthday and reads its contents. When Howard finds out about the letter, he destroys it without bothering to read it and starts acting strangely. The rest of the gang, curious about what was written in the letter, force Sheldon to reveal the letter's contents, as he was the only person who had read the letter. Eventually, Howard finds out that Bernadette and his friends knows about the letter's contents and storms out of a dinner party organized by Leonard and Penny. Later that night, Sheldon figures out a way to reveal the contents of the letter to Howard without letting him actually know what was written in it. He asks the rest of the gang to come up with an account of the letter's contents, with only one of the accounts actually being true; Raj, who speaks first, tells that Howard's father had sent Howard a birthday card; Sheldon tells that the letter contained a map to the lost treasure of the famous pirate One-Eyed Willy, which turns out to be the plot for The Goonies; Amy tells that Howard's father secretly turned up at his son's high school graduation and cried because he was proud of him; Penny tells that the letter explained that the reason Howard's father left his family was that his "other life" caught up with him and left his family as a result to keep them safe; Leonard tells that Howard's father wrote about the importance of family and that Howard should never abandon his family like he did; Bernadette tells that the letter contained a photo of Howard's father holding him as a baby with the words "Howard, my son, my greatest gift". Howard is pleased, wishing that all of the accounts were true, and returns to his happy self.

With the death of Professor Tupperman, a vacancy for a tenured position opens up. Sheldon, Leonard, Raj and Kripke fight for the post and try to impress the head of the tenure committee, who happens to be Janine Davis, the HR administrator of Caltech. Both Leonard and Kripke exercise along with her at the gym in an attempt to talk to her, with Leonard eventually suffering an asthma attack; Raj sends her a 90-minute video about himself; Sheldon gifts her a DVD of the TV miniseries Roots to make up for his racist comments about her in The Egg Salad Equivalency but, puzzled when she clearly doesn't appreciate that either, offends her by asking "you are black, right?". Sheldon, Leonard and Raj eventually decide to attend a memorial service for Professor Tupperman as the tenure committee is going to be there, with Sheldon and Leonard deciding to take Amy and Penny respectively with them to boost their reputation with the committee. When they encounter each other at the memorial service, they lash out at each other, with even Amy and Penny joining in support of their respective boyfriends. The fight stops only when Leonard comes to his senses and realizes that he would rather lose the tenured post than lose his friends. The five decide to return home, but when they see Kripke flattering Mrs. Davis, they attend the memorial anyway. Eventually, Sheldon, Leonard and Raj are shortlisted for the tenured position purely based on their accomplishments. Sheldon thanks Mrs. Davis for shortlisting him, but offends her again by giving her what he believes is a "traditional black handshake".

Recurring characters: John Ross Bowie as Barry Kripke and Regina King as Janine Davis

Sheldon is upset when the SyFy television series Alphas is cancelled on a cliffhanger and unsuccessfully makes calls to the SyFy network to put it back on air. When Amy notices this, she decides to teach him to overcome his "closure" obsession. She leads him through a series of activities, forcefully stopping him from completing the activity just before he is about to finish it. These events make Sheldon furious at Amy, but he hides his true feelings from her and lies to her that he has been cured of his closure obsession. Once Amy leaves, he completes all the activities he was denied from finishing by Amy.

Meanwhile, Leonard, who is concerned that he and Penny do not share any interests, asks Penny to watch Buffy The Vampire Slayer with him, thinking that it could become their common interest. Penny does not enjoy the show, but pretends to like it so that she does not hurt Leonard's feelings. On conversation with Bernadette, Penny reveals that she is not passionate about many things like Leonard, but decides to find an activity she is passionate about. Later, while she is having dinner with Leonard, she finally reveals what she is passionate about: Leonard, as well as his friends, including Sheldon.

Elsewhere, Raj reads Lucy's blog, where Lucy had written about their date. He gets upset when he reads what Lucy had written about him: she had described him as "a little feminine". On conversation with Howard, Howard admits that Raj is effeminate, but asks him to work that out to his advantage with Lucy. Raj refuses to take that advice and tries to behave more manly during a dinner date with Lucy. His "manly" behavior creeps Lucy out. Just as Lucy is about to walk out from their date, Raj reveals what he had seen in her blog. Lucy then admits that he is feminine in a "good way", such as being sweet, thoughtful and having a "skin like caramel".

Recurring character: Kate Micucci as Lucy

When Sheldon and Leonard find out that Dr. Arthur Jefferies aka Professor Proton, who was famous for hosting a children's science show which the two loved when they were kids, is still alive and is available for children's parties and events, they invite him to their apartment to perform a show for them, despite them already being physicists. Professor Proton does accept their invite and arrives the next day, but finds performing a children's science show in front of some physicists weird. He also admits that he has become disillusioned about his TV persona, as despite having a PhD from Cornell University, he was never taken seriously by other scientists. He does seem to enjoy doing his show for Penny, to whom he has taken a liking, but when he sees how ignorant she is about science (he even mentions to Leonard how he and Penny even get along because of their different personalities), he loses interest and starts packing up, though he changes his mind when Sheldon and Leonard motivate him by hailing him and his show as the reason they became physicists in the first place. Following this, he suffers a sudden problem with his pacemaker and is admitted to hospital. At the hospital, Professor Proton asks a visiting Sheldon to perform in a Korean child's birthday in his place the next day as he is not well enough to do so. Sheldon is flattered at this and starts considering Professor Proton as his "father", which he reluctantly goes along with.

Meanwhile, Raj asks Howard and Bernadette to take care of his Yorkshire Terrier Cinnamon while he is at the telescope lab during the weekend. They accept, but end up losing Cinnamon while taking her to the park. Despite frantic searching, they are unable to find her. Eventually, she is found by someone else, who contacts Raj. An infuriated Raj then lambastes Howard and Bernadette for losing Cinnamon, but when they find out that he had already found Cinnamon hours before he contacted them, it becomes Bernadette's turn to lash out at Raj for keeping them worried about Cinnamon despite her already been found.

Recurring character: Bob Newhart as Dr. Arthur Jeffries
Note: Bob Newhart won a Primetime Emmy Award for Outstanding Guest Actor in a Comedy Series for his role of Professor Proton in this episode.

With the girls heading to Las Vegas for the weekend and with Lucy busy, the guys decide to spend their time away from their women by playing a game of Dungeons and Dragons with Howard as the dungeon master instead of Leonard for a change. During the course of their game, Raj receives a message from Lucy which says that she is free, prompting him to leave the game and go on a date with her. Their date goes on well until Raj takes exception to Lucy not complaining to the waiter regarding the crab cakes, following which Lucy walks out of their date by pretending to go to the washroom. But when she comes out of the washroom window, she finds herself trapped in a fenced-in area, prompting her to call Raj for help. Raj does rescue her, but then confronts her over her constantly walking out of their dates. He also adds that he loves her because she has more emotional problems than him, following which they kiss.

Meanwhile, back at Leonard and Sheldon's apartment, the guys' game continues. They are interrupted by the girls, who have cancelled their Vegas trip and returned to the apartment, thanks to Amy assaulting a TSA officer at the airport after she "groped" her, which prevented the trio from boarding their flight to Las Vegas. On Leonard's request, they agree to join their game. The game goes on well until Howard asks the characters of Sheldon and Amy to have sex, which makes Amy upset, as she feels that the others are making fun of her non-sexual relationship with Sheldon, and locks herself in Sheldon's bedroom. Sheldon goes over to his room and consoles Amy, explaining that despite them not having sex, he feels that their relationship is "intimate". He also reveals that he has not ruled out having sex with her one day. Following this, they simulate a sex scene with their game characters.

Recurring character: Kate Micucci as Lucy
Guest star: David Trice as Waiter

Stephen Hawking's team is sending an expedition to the North Sea to find the hydrodynamic equivalent of Unruh radiation. On Howard's recommendation, Leonard joins as a member of the expedition, but is worried about leaving Penny for four months. Penny gives him the green light to go. Sheldon, on the other hand, is jealous of his best friend's new career opportunity and coupled with his fear of being alone for four months, tries to dissuade Leonard from going, to no avail. On Penny's advice, Sheldon decides to drop his hard feelings for Leonard, eventually giving a happy and supportive toast to him at his bon voyage party.

Meanwhile, the guys ask Raj to introduce Lucy to them. Since Lucy is extremely uncomfortable with meeting new people, Raj plans on introducing only one member of their gang to her at first. The honor falls on Amy, the newest member of their group. Although Amy initially handles Lucy reasonably well, Raj begins to demand to know about the status of their relationship, and this causes her to lock herself in the bathroom. Raj eventually asks her to attend Leonard's bon voyage party, to which she reluctantly agrees. But, instead of attending the party, she breaks up with him through a text message while he is at the party, which reduces him to tears. Later, after dropping Leonard off at the airport, Penny goes over to Raj's apartment and tries to console him. When Raj says that he is unlovable, Penny mentions that he is saying that because he is drunk, but then Raj reveals that he did not drink any alcohol since he broke up with Lucy. At this revelation, both of them are amazed and happy, since Raj has finally overcome his selective mutism. The episode ends with Raj talking non-stop about Lucy to the women, much to their annoyance.

Recurring character: Kate Micucci as Lucy