Other mistake: The date on the tombstone above Annie says that Judith Myers was born November 10, 1947, and died October 31, 1963. That would make her 15 (not quite 16 yet) at the time of death, yet everyone says that she was 17 years old.
Other mistake: In the aerial shots of the semis being driven in the mall parking lot, the zombies are milling about. Notice they have left a path just clear enough for the truck. (01:02:40)
Other mistake: In every case, the pod needs hours to take over the human, but, in Elizabeth's case, she gets changed in less than 5 minutes. (01:24:00)
Other mistake: When the shark grabs and eats Marge, there is no blood at all.
Other mistake: Fred MacMurray is listed as "Clarence" in the closing credits, but when he is standing outside his store and talking to Maureen, a promotional sign in the background spells his name as "Clarance."