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.
Correction: There are bound to be more survivors than Regina's gang. This couldn't be one of them?
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.
Correction: Self correcting mistake. "Most" of the population isn't ALL - the car might have been abandoned a few minutes before they arrive. (Perhaps by someone scared off by the sight of two strange girls waving machine guns about?).
Correction: Could have been another survivor wandering around. After just being attacked by a comet zombie Regina ain't gonna stop to check!
Grumpy Scot