SpongeBob SquarePants

The Tenth Doctor mentioned SpongeBob SquarePants when Rose Tyler asked him if all stories were based on disappearing time traces. (PROSE: The Stone Rose)

Rory Williams referred to Francesco as a "big, stupid, great Spongebob." (TV: The Vampires of Venice)

Behind the scenes
David Arnold composed music for the series from 1999 to 2001.

Christopher Ryan and Nigel Planer both made guest appearances in the episode "Chimps Ahoy".

Robin Sachs made a guest appearance in the episode "Mrs. Puff, You're Fired".