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Sheldon hosts Judy Greer's character, who is a renowned physicist interviewing at the university. On her first night in Pasadena, she hits on Leonard and ends up sleeping with him... much to Sheldon's shock, when Penny, needing a ride to work the next morning, recognizes the guilty look on Leonard's face and calls him out on having slept with her. Leonard tries to boast about having slept with her over lunch, though she then hints that she wants Raj. Ultimately, she tries to get Raj, Howard and Leonard into some role-playing sex games when Halo Night moves to Raj's place because he is "sick." It struck me as about as risque as they could get for pre-10pm tv, and while shows can be funnier when watched in groups, I think this one would have held up for me on its own, although I guess I can let you know Monday.