The Big Bang TheorySeries 1 Episode 7: The Dumpling Paradox
When Wolowitz seduces Penny's friend and ends up having sex with her in Penny's apartment, Penny sleeps on Leonard and Sheldon's couch. Meanwhile, with Wolowitz occupied, the guys discover that they are without a fourth member of their group. In desperation, they ask Penny to join one of their two-person Halo teams.
- Original air date