Character mistake: When Edward leaves Forks, he does it because he believes that he will be protecting Bella. Except that he seemed to have forgotten that Victoria was still in Forks and was intent on killing Bella.
Character mistake: About 3/4 of the way through the movie, when Jennifer Aniston is talking to Ben Affleck, she calls him Ben instead of his character's name Neil.
Character mistake: Just after the birth of Mona's child, Farhan recollects "uss waqt agar Virus kehta kay mera pouta engineer.". In fact the child is not his "pouta" but his "nata"
Character mistake: If you ever called a Marine Sergeant Major "Sarge", he would probably kill you. It just wouldn't happen. That's an Army thing. Also, Marines say "ooh-rah", not "hoo-ah". That's also an Army thing.
Character mistake: The Finnish businessman says something along the line of "As Scandinavians - we like her". Scandinavia includes Norway, Sweden and Denmark, never Finland (or Iceland); a Finn would know that.