The Lunar Excitation
The Big Bang Theory Season 3 Episode 23 (05/24/10)
After Leonard ruins regular guys for Penny, she comes over to his apartment after a bad date with a moron for some drunken sex with Leonard. The poor guy takes it as a sign she wants to get back together, but she breaks his fragile little heart again. He heads over to Leslie's for a booty call, fails, heads back to Penny's for one and fails again.
Meanwhile, Raj and Wolowitz create an online dating profile for Sheldon and it finds him a perfect match. They blackmail Sheldon into going on the date where he meets the female version of him: Amy (Mayim Bialik).