In season 6, 'The God Complex' The Doctor, Amy and Rita are running after the 'bad guy',
DOCTOR: Stay back!
(The Minotaur smashes a glass door and knocks Rory down.)
DOCTOR: Pond, bring the fish.
AMY: What, the fish? Oh, the fish.
What does he mean? This has been bothering me for a while now. Maybe I just don't get the joke, because I don't speak English as my first language..