Season 4: Episode 84: The One With Phoebe's Uterus
Frank Jr. and Alice, having just eloped, ask Phoebe to be a surrogate mother for them. When Phoebe asks her birth mother for advice, Phoebe Sr. gives her daughter a puppy for a few days so she can see how difficult it is to give up something you love. Phoebe can't decide whether she's going to go through with the surrogacy - that is, until she gives Frank and Alice the puppy and sees how happy they are. If they're that happy over Phoebe giving them a puppy, how happy will they be when she gives them a child. Meanwhile, Ross gets Joey a job as a tour guide at the museum. At lunch Ross won't sit with his friend (the white coats don't sit with the blue blazers). Ross and Joey take a stand in the cafeteria, but they end up starting something that was better off left alone. Chandler, nervous about getting intimate with Kathy after she's been with Joey, asks the girls for advice and ends up hitting a home run.