Kyle Trager (Matt Dallas) is the main character, a teenage boy with no bellybutton and no memory of who he is or how he got there. His strange case is referred to Nicole Trager, a therapist who takes him home. Kyle must learn to do everyday things like eat and drink, speak, and avoid hurting himself. Season 1 follows Kyle as he learns about how people live, but nothing of who he is. Season 2 answers how and why he exists, and begins his efforts toward what he is supposed to do.
Nicole Trager (Marguerite MacIntyre) is the psychologist who takes in Kyle as a foster child as well as a patient for his "amnesia". She is married to Stephen Trager, with an older daughter Lori and son Josh. Nicole is Kyle's main help and moral anchor throughout the series.
Stephen Trager (Bruce Thomas) is Nicole's husband. He is a well-paid software designer who directs a programming team. Stephen and Nicole are happily married, healthy, and permissively supportive of the kids.
Lori Trager (April Matson) is the teenage daughter of Stephen and Nicole, the older sister of Josh and then of Kyle who is her age. Lori sneaks out to date Declan and get drunk at parties. She loves Declan, but their romance is on and off. Lori confides in and fights with her only other friend, Hillary.
Josh Trager (Jean-Luc Bilodeau) is the son of Nicole and Stephen Trager, the younger brother of Lori and then Kyle. Josh is more interested in pornography than school, and is devoted to "G-Force" online gaming. He introduces Kyle to basketball. During season 1 he must first get into high school and then get out of remedial classes. Josh is scheming and mercenary, and accidentally predictive about Kyle.
Declan McDonough (Chris Olivero) is a spoiled rich-kid and high school basketball star. He is soon the ex-boyfriend of Lori Trager, yet remains in love with her through the series. Declan's best friend is Charlie Tanner. He also becomes close friends with Kyle, sharing Kyle's secrets and adventures through the series.
Amanda Bloom (Kirsten Prout) is "the girl next-door" to the Tragers. Kyle is drawn to the sound of her piano and immediately is in love with her. She also feels an attraction to Kyle, but her mother tries to keep them apart. Kyle is afraid that Amanda will not like him the same if she knows of his origins, yet she learns of many of his strange ways and abilities. Their romance continues through the series.
Jessi (Jaimie Alexander) arrives in the world in the same way as Kyle, but shows a very different personality. Overcoming that and her early experiences is her story, and is increasingly part of Kyle's story.
Recurring Characters
Tom Foss (Nicholas Lea) is the villain of season 1, stalking Kyle in an old red truck. As we learn more about him, and how dangerous he really is, he becomes pivotal to the story, and to Kyle, through season 2.
Carol Bloom (Teryl Rothery) is the mother of Amanda Bloom, next door to the Tragers. She has a bad first impression of Kyle and other bad impressions afterwards. She tries to prevent their romance, but relents some of the time.
Hillary Shepard (Chelan Simmons) is very blonde, very nicely built, and very vivacious. She is the best friend of Lori, when they are not fighting. She makes a career decision in season 2 that has unexpected consequences for all the Trager kids.
Charlie Tanner (Cory Monteith) is Declan's best friend and the basketball team captain. He is the boyfriend of Amanda who keeps Kyle from directly pursuing her. We, and eventually she, find out more about his activities in season 2.
Bradford Hooper (Malcolm Stewart) is the principal at Beachwood High School. He is proper and strict, and a lot of trouble for all the Trager kids.
Andy Jensen (Magda Apanowicz) meets Josh when he is working at The Rack coffee shop. They had aleady been online gaming competitors, with 'andyJ' always winning. They next meet in school, and are soon meeting any time they can. She was raised by lesbian mothers and is revealed to have terminal cancer, though Kyle somehow manages to cure it.
Mark (Josh Zuckerman) is a student at UW that Lori meets by accident at The Rack. She finds out too late that he is her father's teaching assistant. She wants his help with music, and he offers her more than she asks for. She accepts, with some conditions, and Declan is right to be jealous.
Season 1 Characters
Lou Daniels (Dorian Harewood) directs the Juvenile Detention Center where the naked boy is taken when arrested. He calls Nicole about the strange case, knowing that is her specialty. Lou says that the boy's "good looks" remind him of his brother, Kyle. When the boy responds to the name, Nicole decides to call him that.
Detective Jason Breen (Kurt Max Runte) is assigned to Kyle as a Missing Persons case. He must contact Kyle and the Tragers repeatedly with further developments.
L.K. Deichman (Cascy Beddow) is a nerdy boy called "geekman" and "dykeman" whom Kyle meets at lunch his first day at high school. They share an interest in drawing, and L.K. helps Kyle by showing him the library.
Toby Neuwirth (Calum Worthy) has "major anger management issues." He is in the remedial English class with Josh his first day in high school. Toby feels insulted by Josh in class, and is a lot bigger than Josh.
Wes (Brendan Penny) meets Lori when she is visiting UW with Kyle and Declan. He likes her and they spend more time together than Declan likes.
William Kern (Bill Dow) was a science professor at the University of Washington. He taught Baylin and was then recruited by Baylin to work at Zzyzx. He was in charge of "781227".
Dennis Bunker (Mackenzie Gray) works in personnel at Zzyzx. When Foss resigns, Bunker puts some details together that could be valuable.
Rebecca Thatcher (Sarah-Jane Redmond) is an official at Zzyzx, rather than a scientist like Kern. She is the boss of Cyrus Reynolds.
Cyrus Reynolds (Andrew Jackson) is the director of security of Zzyzx. Rebecca sends him to correct a threat to their secrecy.
David and Julie Peterson (Ken Tremblett and Carrie Genzel) present themselves as Kyle's birth parents at the end of season 1. "Julie" strongly resembles Kyle, and they have a full explanation of how "Noah" was abducted and lost to them for five years. When Tom Foss explains their roles, Kyle plays his role too.
Season 2 Characters
Adam Baylin (J. Eddie Peck) was the creator of Zzyzx as a research facility for an experiment in artificial gestation. His connection to Kyle is revealed in season 3, when a lot of answers are presented—by a very dangerous accident, as well as by Adam's careful plans.
Brian Taylor (Martin Cummins) grew up with Adam Baylin and remained his close but not entirely trusted friend. Brian had a competing experiment that Adam did not know about, and returns to control the outcome.
Julian Ballantine (Conrad Coates) is an executive at MadaCorp. Discovering that both "assets" from Zzyzx are alive, he wants both dead, but only after retrieving the priceless data "781227" has from Zzyzx. The plan involves Emily Hollander involving "781228" with the Tragers.
Emily Hollander (Leah Cairns) works on secret missions for MadaCorp under Ballantine. She does what she is told to do with Jessi, because she is under threat too.
Paige Hollander (Nicole Leduc) is the young daughter of Emily Hollander.
Anna Manfredi (Eileen Pedde) still works at UW where she had been Kern's research assistant. She helps Kyle with his search for information about his possible connection to Kern and Baylin.
Sarah Emerson (Ally Sheedy) was Adam Baylin's college girlfriend. She contributed to the experiments at Zzyzx, but was absent and presumed dead afterwards.
Season 3 Characters
Michael Cassidy (Hal Ozsan) serves as a director of Latnok and of a group of exceptional students doing creative science projects in a special facility at UW that is funded by Latnok. He is determined to convince Kyle to join with Latnok, and will stop at nothing to get what he wants.
Nate (Jesse Hutch) is introduced to Kyle as Nathaniel Harrison, an important member of the student Latnok club at UW. His competition with Kyle includes Amanda.
Jackie (Ali Liebert) is another student in the UW Latnok club. She is the first student Kyle meets. She meets Declan at their club party, and they seem to have similar "chemistry".