The Dumpling Paradox
'The Dumpling Paradox' - Season 1, Episode 7
Penny's promiscuous friend from Nebraska is in town and Wolowitz quickly seduces her, taking over Penny's apartment in the process. Penny takes refuge on Sheldon and Leonard's couch. With Wolowitz otherwise engaged, the guys enlist Penny as the fourth member of their Halo team.
Air Date: November 5, 2007.