The Cast Went To a Real Frat Party
… And ended up getting beat up by rough and tough football players.
The cast wanted to completely submerge themselves into their roles, and part of this method was to attend a real frat party on the University of Oregon campus.
Source: NY Times
True story: a group of college girls invited them to a mixer (party) thrown at a “wealthy jock fraternity,” but things turned ugly very soon. After a bunch of drunk football players called them some nasty words, actor James Widdoes (Hoover) threw a beer and started a full-on brawl. Actor Bruce McGill (D-Day) got a black eye but was too embarrassed to tell director John Landis what happened. But Landis eventually found out what his cast had been up to.