Trivia: The moment where Blutarski breaks the guitar and then apologises was unscripted, and improvised by John Belushi.
Trivia: During the scene where John Belushi is sneaking around, you see him slip and then get back up. The slip was accidental but the film makers left it in the movie.
Trivia: Faber college, where the movie takes place, was actually the University of Oregon in Eugene.
Trivia: On a budget of only $3 million, the producers offered actor Donald Sutherland a choice of $35,000 cash for 2 days work or 2% of the film's box office gross. Because nobody in the cast or crew believed that "Animal House" would be a hit, Sutherland opted for the $35,000 cash. As it happened, the $3 million comedy went on to gross over $141 million at the box office. Meaning that Sutherland would've made $2.8 million if he had chosen 2% of the gross.
Trivia: Bit of an in-reference: At the end of the film when we are brought up to date on each character, we are told that Lt. Niedermayer is shot by his own men in Vietnam. In the movie Twilight Zone: The Movie (1983), during the segment directed by John Landis, one of the American soldiers in Vietnam says "I told you guys we shouldn't have shot Lt. Neidermayer".
Trivia: Sean McCartin, who played the boy who thanks God after a sorority girl ends up in his room dressed like a Playboy model, went on to become a pastor at a local church in Cottage Grove, Oregon. The headline on a newspaper read, "'Lucky Boy' Still Thanking God."
Trivia: Dan Aykroyd was suppose to play D-Day but he couldn't get out of his SNL contract. Ironically, D-Day was based on Aykroyd.
Trivia: The saying under the Delta flag is the saying for MGM studios.
Trivia: John Belushi was originally supposed to co-star with fellow SNLers Chevy Chase, Bill Murray, Dan Aykroyd, and Larraine Newman (as Otter, Boon, D-Day, and Katie, respectively). All backed out due to prior commitments.
Trivia: Animal House has been credited with reversing a decade-long decline in fraternity enrollment on college campuses.
Trivia: Several of the film's stars reprised their roles in the short-lived spin-off sitcom "Delta House."
Trivia: 18-year-old actress Sarah Holcomb started her movie career in 1978's "Animal House" (playing Clorette DePasto, the mayor's 13-year-old daughter) and ended her movie career two years later in 1980's "Caddyshack" (playing the fiery Maggie O'Hooligan). Holcomb actually appeared in five films during her two-year career, which came to an abrupt end due to severe schizophrenia brought about by cocaine addiction. Holcomb was institutionalized and never returned to acting. Today, at age 58, Holcomb lives a quiet, reclusive life under an assumed name somewhere in Connecticut.
Answer: Sometimes these things get left in because it's simply the best take. (The child covering his ears before the gunshot in "North by Northwest," for example.) It could also be that John Landis cast the extra because he wanted someone with goofy expressions in the crowd. He simply could have told the extras "Ok, be excited that you're at a parade," and that's how this extra did it.
Captain Defenestrator