When Penny locks herself out of the apartment, she comes to hang out with Sheldon in his as he plays Age of Conan. Penny, frustrated by her recent failures in life soon plays and becomes addicted to Conan.
It's very simple. 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
Sheldon [to Kripke]: Also, I am given to understand that your mother is overweight. Raj: Oh, snap. Sheldon: Now of course, if that is the result of a glandular condition and not sloth and gluttony then I withdraw that comment.