Friends

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.

Because of a bet between Matthew Perry and Bruce Willis on the set of Falsas apariencias (2000) (which Perry won), Willis appeared in his three-episode guest role for free. Willis went on to win an Emmy for his guest role in Friends (1994).

Lisa Kudrow based her hippie character Phoebe on her co-star Jennifer Aniston - because of the actress' interest in "spiritual" subjects.