Penny brings in Chinese for the guys and hangs out in her sweats. Don't worry, for now Wolowitz still thinks she looks ravishing. It's only when the new neighbor shows up does Penny need to step it up.
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