When trying out for the role of the altar boy, Edward Norton went into the audition in character, complete with stutters and all, and this won his role.
2,100 actors auditioned for the role of Aaron Stampler - Matt Damon was one of them.
Both Wil Wheaton and Leonardo DiCaprio turned down the part of Aaron Stempler. Wheaton turned down the role because he didn't want to put off his acting school and when his manager urged him to take the role anyway he told him "It is like Luke Skywalker when Yoda told him not to go and save his friends but to stay on Dagobah and learn to be a Jedi instead. Luke didn't listen to him and that's why he never became true Jedi master." Later Wil Wheaton regretted turning this role down, saying that this was a crucial factor why his career never got to be a successful one.