Rock Paper Scissors Lizard Spock was invented by Sam Kass with Karen Bryla, years before television made it famous. It became widely known after Sheldon Cooper explained it in The Big Bang Theory season 2 episode "The Lizard-Spock Expansion", which aired in 2008.
Who created it and why
Sam Kass is a software engineer who published the rules, with a diagram, on his personal website. He credits Karen Bryla as co-creator. His explanation for the game is practical rather than whimsical: when two people know each other well, a large share of their ordinary Rock Paper Scissors games end in ties, because they fall into the same habits. Kass puts the figure at 75 to 80 percent for people who know each other well. That is his own observation, not a measured study, but anyone who has played a sibling will recognise the problem.
Adding two more throws fixes it mathematically. With five options, two random players tie one time in five rather than one time in three. Kass also jokes on his page that the five-throw version satisfies the "Law of Fives".
The two new throws:
- Lizard: the hand shaped like a sock puppet's mouth.
- Spock: the Vulcan salute from Star Trek, fingers split between middle and ring.
The rules in one breath
Scissors cuts paper, paper covers rock, rock crushes lizard, lizard poisons Spock, Spock smashes scissors, scissors decapitates lizard, lizard eats paper, paper disproves Spock, Spock vaporizes rock, and, as it always has, rock crushes scissors.
Each throw beats two and loses to two. The full table and a printable chart are on our Lizard Spock rules page.
How The Big Bang Theory made it famous
In "The Lizard-Spock Expansion" (season 2, episode 8, 2008), Sheldon proposes the game to settle a dispute and recites the full list of outcomes in one rapid speech. The scene was short, but the speech was exactly the kind of thing fans memorize and quote, and it spread from there onto T-shirts, posters and classroom walls.
Kass has acknowledged the show on his site with a thank-you to the programme. Most people who play the game today learned it from the show and have never heard his name, which is a common fate for game inventors.
Why it caught on online
A few things helped the game outlive a single TV scene:
- It is instantly checkable. You can learn it from one diagram.
- It fixes a real annoyance. Fewer ties is a genuine improvement, not a gimmick.
- It is a nerd in-joke. Knowing it signals you get the reference.
- It is a classic coding exercise. Beginner programming courses often use it once students have built the three-throw version, because the five-way logic is a good test of clean conditionals.
Common myths
- "The Big Bang Theory writers invented it." No. Kass and Bryla created it first; the show adopted it.
- "It's an official version of Rock Paper Scissors." No variant is official. It is one popular house rule among many; see our variations guide.
- "It makes the game more skilful." It reduces ties. Whether it rewards skill more is debated, since with more options there are more patterns to hide and to read.
For the history of the original three-throw game, see our history page. You can also practise the classic version and play free online.
FAQ
Who invented Rock Paper Scissors Lizard Spock?
Sam Kass, with Karen Bryla.
What episode of The Big Bang Theory features it?
"The Lizard-Spock Expansion", season 2, episode 8, first broadcast in 2008.
Why add Lizard and Spock?
To cut down ties between players who know each other's habits. Five options make a tie less likely than three.