It’s Christmas in March! Peter Billingsley, who played Ralphie in A Christmas Story (1983), also made a brief (although uncredited) appearance as Ming Ming the elf in Elf (2003), starring Will Ferrell.
Old School wasn’t the only time Will Ferrell hung around a college campus. He appeared in an episode of Undeclared as Dave, a guy who sells pre-written essays to college students, and, fortunately, keeps his clothes on much more than his character from Old School.
Like Ferrell’s character, I once had a job selling lecture notes, but was fired because apparently writing down things like “useless nonsense” isn’t helpful.