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.

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).

Joey's statue of a white dog was originally given to Jennifer Aniston as a good luck present from her best friend when she started acting. She offered to lend it to the show for the episode where Joey became rich and bought a lot of stuff. After that episode, the producers decided to keep it.