Visible crew/equipment: When Roger hits the zombie with the truck, notice at the bottom right a trampoline from which the zombie jumps off. (01:04:55)
Visible crew/equipment: When the two kids in the airport attack Peter and try to bite him, notice in the top right corner a crewmember's hand comes into shot. (00:25:40)
Factual error: When they are refuelling the helicopter (as a zombie approaches quietly from behind) the actor has put the gas nozzle not into the hole for the gas tank, but into one of the foot-holes that helicopter mechanics use to climb up to the top of the helicopter to do repairs. It doesn't even fit properly. (00:22:55)
Visible crew/equipment: In the rural airport scene a zombie is killed as Roger is filling the helicopter with fuel. As the zombie falls off the boxes, the tubing that pumped the blood is coming out of his pantleg. (From the Divimax widescreen DVD) (00:24:00)
Answer: One of the cops that was with Joe Plato (how much you have seen of them will depend on which version of the movie you, but I HIGHLY recommend the fan made/edited 'Extended Mall Hours' cut on YouTube) asked them for cigarettes. You'll notice that Roger and Fran lit up cigarettes as they were taking off, that's what Roger was laughing at.