Friends Season 2 Episode 6 : The One with the Baby on the Bus
When Ross has an allergic reaction to Monica's kiwi-lime pie, Chandler and Joey are asked to baby-sit Ross's son, Ben. While using Ben to help them try to pick up girls, they accidentally leave him on a bus. Although they later locate him, they are not sure the baby is really Ben. Phoebe loses her Central Perk singing gig to a professional singer (Chrissie Hynde), and she becomes a street singer in front of the café.