The One with Phoebe's Uterus Friends : Season 4 Episode 11

Phoebe considers her options when her brother visits with his new wife and asks her to carry their child. Joey works as a tour guide at Ross's museum and tries to tear down the walls between tour guides and scientists. And Chandler seeks advice from Monica and Rachel after he fears that he will not live up to Kathy's sexual expectations--especially since the last guy she slept with before him was Joey.