Dan Aykroyd turned down the role of D-Day due to a prior commitment. The role was reportedly written with him in mind.

Director John Landis wanted to cast Chevy Chase as Otter, but he had a scheduling conflict.

If John Belushi would have refused the part of Bluto, Meat Loaf was going to be the next pick.

Animal House was set to be filmed at the University of Missouri until the president read the script. Then the university of Oregon reluctantly allowed the use of their campus but limited them to just 30 days of filming.

The director's original choice for Boon was Bill Murray, but he was commited to another project.

Novak was the original choice to play Dean Wormer's wife.

Webb was the original choice to play Dean Wormer.