Rock-paper-scissors-lizard-Spock is a five-gesture expansion of the classic selection method game rock-paper-scissors. It operates on the same basic principle, but includes two additional weapons: the lizard (formed by the hand as a sock-puppet-like mouth) and Spock (formed by the Star Trek Vulcan salute). This reduces the chances of a round ending in a tie compared to the more traditional game. The game was originally invented by Sam Kass and Karen Bryla.[1] It was mentioned in an article of The Times in 2005,[2] and popularized in 2008 by "The Lizard-Spock Expansion", the 8th episode, Season 2 of the sitcom The Big Bang Theory. In that episode, Sheldon introduces the game to his friends and, being avid fans of Star Trek, they all continuously put up the "Spock" sign.
The rules of Rock-paper-scissors-lizard-Spock are as follows:
There are ten possible pairings of the five gestures, where each gesture beats two of the other gestures and is beaten by the remaining two.