The Cast Stayed In Character Throughout the Whole Film
… And treated each other like frat enemies.
Before all the partying even began, John Landis got all the actors playing Delta frat guys to meet and begin bonding five days before the filming began. They called each other by their character’s names and even painted the Delta house with the graffiti that you saw in the film.
Copyright: Universal Pictures
And then when the cast playing the Omega frat boys joined them, they were treated as enemies. Mark Metcalf (Neidermeyer) even remembered the food being thrown at him. Metcalf later revealed that he chose to hang out in his motel room while the others partied so he could “ listen to all this partying to get into character. I would sit up there and spit polish my riding boots and brood and make plans for what I could do to get revenge on them for their decadent way of life .”