Other mistake: The movie starts in September 1961 and we are told that the talent show is in June. During the talent show there's a big banner saying 1961 when it should read 1962.
Other mistake: When McCroskey gets the information about Joe Seluchi, he's told that Seluchi purchased life insurance and was impotent. McCroskey informs Ted about Seluchi and the bomb he's carrying but nothing else. When Ted confronts Seluchi, he mentions both the insurance and the impotence.
Other mistake: Rattner and DiMone are game planning about Rattner's date with Stacy (Leigh). DiMone tells Rattner that all he needs to do to score with Stacy is play songs from side 1 of "Led Zeppelin IV" (Zoso). You then hear the song "Kashmere", which is on the album "Physical Graffiti".
Suggested correction: Damone (not DiMone), told Rat that when they were making out to put on side 1 of Led Zeppelin IV. The fact that Rat is playing Kashmir from Physical Graffiti is just to show that Rat was unclear about Damone's instructions.
Not sure if Rat is unclear about Damone's instructions... he said he had 4 steps to making sure that getting a date with Stacy and keeping her around, and if all else fails, to play side one of LZ-IV... seems that Rat would (should) have asked if he was unclear then at that point considering Rat had a crush on her throughout the movie. I think that it's more of a musical inside joke if anyone was/is familiar with the Zep catalog realizing two things - one, the first four steps of Damone's plan didn't work being that his character was pretty shady and fake (off camera...because you don't see Rat implementing any of them) and two, that "he can't even get the music correct" due to his nervousness.
Other mistake: When Sid committed suicide, the coroner brought him out of the office...not his room.