Taxi - Season 3 Episode 10 : The Costume Party 1983

Bobby finds a fancy briefcase in the back of his cab, and when the cabbies are going through it, with the intention of returning it to its rightful owner, they find an appointment book that shows appointments with various celebrities. They also find an invitation to a cocktail party on a yacht. Thinking that this is their chance to meet celebrities, they dress up and crash the cocktail party, and are soon star struck with costumed people they think are stars. They eventually realize that it's a party for realtors (who evidently have famous clients) and they leave, disappointed.