Character mistake: During the scene in which they are all arguing whether or not film sequels are better than the original or not, someone says Sigourney Weaver's classic line from the movie Aliens: "Get away from her you bitch", and Randy makes a smart comeback and tries to correct him by saying "I think the correct line was 'stay away from her you bitch'. This is a film class, right?" Wrong - the first guy was right. This line is truly unconvincing for the Randy character, being a big movie buff and all. Jamie Kennedy decided to improvise as Joshua Jackson actually made the initial mistake by saying the wrong line, causing a different mistake. (00:16:25)
Character mistake: When Nicolas returns from Mexico and goes to the gate of his house, he sees a sign that says his house is being sold at public auction. The word "foreclosure" is spelled incorrectly. It is spelled "forclosure."
Character mistake: When they first receive the alien signal, they decode it and play it as a TV signal which shows Hitler speaking at the opening of the 1936 Summer Olympics in Berlin. Kent translates what Hitler is saying as "I declare the Games in Berlin, at the celebration of the first Olympics of the New Era, as opened." Hitler actually says "the *eleventh* Olympics of the New Era." The "New Era" doesn't refer to some Nazi concept, it's used to separate the modern Olympics from the ancient ones in Greece.
Character mistake: Casanova refers to Cross's gun as a "Glock," but it is a Sig.
Character mistake: White says Exley's father died in the line of duty. Exley said he was off duty when he was shot, and he didn't correct him.