Corrected entry: When Regina is first driving the bike and rounds the corner of the shiny marble building, you can see someone's reflection on the right side of the building, walking around.
Corrected entry: After the comet passes, and the sun rises and we see deserted streets. The third shot in, we see some construction equipment in the street. On the far right side you can see someone walking out of the building in the entire shot.
Corrected entry: A few days after the comet wipes out most of the population, the two girls test their machine guns by shooting up a parked Cadillac. Steam from the radiator pours from under the hood. Highly unlikely - if the car was sitting for more than a few hours, the coolant in the radiator would not be hot enough to make steam.