The cast were not informed of the identity of the killer until the last day of principal photography. Also, the cast did not receive the last ten pages of the shooting script until it was time to film the scenes contained therein. Furthermore, the last ten pages of the shooting script were printed on gray paper in order to deter illicit duplication of them. All cast members were required to sign confidentiality clauses as parts of their respective contracts that precluded them from discussing the outcome of the story and the killer's identity.
(At around one minute) Paulette Patterson, who plays the usher who hands masks to Maureen (Jada Pinkett Smith) and Phil (Omar Epps), won her role in a contest sponsored by MTV.
There's a scene earlier on in the movie when Sidney confronts Randy, as they're walking to class, about the killings on campus, and insists it's another killing spree, all over again. And at that point Randy inexplicably switches to an English accent for part of the scene. In a recent podcast Jamie Kennedy burst into laughing when he watched the scene and admitted he had no reason why Randy would suddenly switch accents like that. According to the commentary, this was an impersonation of the line producer on set.
Contrary to the mention of his name, Robert Rodriguez did not direct the scenes of "Stab", the movie-within-a-movie. They were instead directed by the Scream 2's director, Wes Craven. This is why Rodriguez's name does not appear in the actual credits for the film, and only within the movie itself.