Gorchestopher's answer is very accurate, but I'd like to add a little contribution. In "The Why of Fry" (S05E08), when Fry is trapped inside the Infosphere, the Giant Brain suggests he query the database concerning the night of December 31st 1999 (the date Fry got frozen). Fry then finds out that it was Nibbler who deliberately blew Fry's tilting chair, which made him lose his balance and the chair tipped back. They have an argument: Fry: I, I don't understand. You made me go in the freezer tube?
