Friends

In the opening credits to Friends: The One After Vegas (1999), all of the names in the opening (actors and crew) were changed to have "Arquette" at the end of them, a gag on Courteney Cox Arquette who had just recently married David Arquette.

The episode where Phoebe thinks her dead mother has been reincarnated as a cat was written by Marta Kauffman at the time when her own mother recently passed away (the episode was dedicated to her). In an interview with one of the other writers, they admitted that said this would have gotten shot down at the table read, but nobody felt comfortable saying "no" under the circumstances.

The artwork in Central Perk is changed every three episodes.