Ross is a allergic to kiwi. He has an allergic reaction to Monica's kiwi and lime pie (not to be confused with key lime pie). Chandler and Joey offer to take care of Ben while Monica and Ross go to the hospital. Ross reluctantly agrees because he has no choice.
Monica and Ross rush off to the hospital. Ross doesn’t like to get shots, so he acts like a child when the doctor tries to give him a shot for his allergic reaction. When he finally gets the shot, he squeezes Monica's hand too tightly, acting as if he’s in excruciating pain.
On the street, Chandler and Joey take care of the baby. Joey thinks they can use Ben for bait to attract girls. A nice lady sees them, but she mistakes them for a gay couple. She congratulates them for their courage. Later, two pretty girls are getting on the bus and Chandler and Joey follow them. On the bus, after Joey makes sure the girls know they’re not gay, they all decide to go out for a drink. When they get off the bus, the guys realize they left Ben on the bus. They try to catch the bus, but it's too fast.
Terry, the boss at Central Perk, tells Rachel to tell Phoebe that a professional singer, Stephanie, is taking her place and getting paid for it as well. Phoebe is upset, so Rachel goes and begs Terry to let Phoebe perform also. Terry decides Phoebe can perform after Stephanie. Phoebe changes her mind when she learns she won't get paid, so she decides to sing on the streets for money. Rachel comforts her by telling her that her favorite song is “Smelly Cat.”
After calling Transit Authority, Joey and Chandler find out where to go to get Ben. Unfortunately, Ben and another baby look alike. To decide which baby to take, they flip a coin. When they get back to Monica apartment, they know they have the right baby because he cries in Monica's arms. Ross wants to change the diaper, and notices that it says "Property of Human Services." Ross goes after the two of them and Chandler tells Joey to run while he fends off Ross with a plate of kiwi pie.
Phoebe has decide that she prefers singing for free rather than for money. She joins Stephanie on the couch and teaches her to play and sing “Smelly Cat."