Plot hole: At the beginning when the SWAT team breaks through the door in the basement and all the zombies escape they don't attack the SWAT team they just run up the stairs.
Continuity mistake: When Peter and Roger are looting one of the stores, Peter brings out the two wheeled cart, which is aluminium colored first. After the shot where Steven is shown in the basement, the cart is now lime green.
Revealing mistake: When the lorries are being moved to block the entrance to the shopping centre you can see on the left in the lorry park cars driving on the freeway.
Continuity mistake: Watch when Sledge swings down from the balcony. In one quick shot, we see that there are two zombies in front of the store "Carlton's." When the shot changes to show Sledge landing, a third zombie has appeared from nowhere.
Continuity mistake: Immediately after the three men close the first door, when they are driving away Flyboy can be seen in the trunk aiming a handgun. It cuts to his face and he's holding a radio, talking to Fran. (01:18:10)
Continuity mistake: When the raiders enter the mall you see Blades (Tom Savini) enter the mall and run around, although when it shows the bikers outside the mall Blades is sitting on top of the red van. (01:46:30 - 01:47:30)
Continuity mistake: When Peter has just killed the child zombies and another with a messed face is in the doorway, we see Steven outside aiming a rifle and it is cloudy, dreary weather. Peter dives out the way and lands by a window and we see that it is now pitch black, then Roger steps in and shoots the zombie from outside and it's only just overcast.
Revealing mistake: When the SWAT team breaks the door in the basement and all the zombies escape,the SWAT team member to the far right is laughing.
Revealing mistake: When they lock the mall doors using the car, Peter is giving cover fire while the doors are being locked. Notice when the camera cuts to one of the shots from the scopes point of view he blows a zombie's head off and the blood splatters on the scope and is visible when the zombie drops.
Other mistake: During the truck scene, when zombies attack Roger the first time, as Peter shoots the zombie that Roger is fighting, he supports his M16 from its carrying handle, thus blocking the rear sight (which is located in said handle). He does this in several scenes throughout the movie, but in the truck scene accuracy is crucial.
Continuity mistake: Just after the raiders manage to get into the mall, one raider uses his sledgehammer to knock a zombie wearing a black t-shirt off his feet. 5 seconds later, the same zombie can be seen walking past the same raider.
Other mistake: On the initial trip to Penneys in the Mall, a zombie manages to get through the door. After Peter closes the door Roger shoots the zombie, the bullet goes through his head as the exit blood spatter suggests, but there's no entry wound.
Continuity mistake: At the end of the movie when Peter is running to the helicopter it changes from night to day in an instant.
Visible crew/equipment: When Peter is attacked coming out of a doorway (after he leaves the boiler room) he wrestles with two zombies. If you pay attention to the bottom of the screen, just before he pushes the zombies away, you can see the hands of a crew member come into the frame. They were probably making sure none of the zombie actors fell into the camera. 2003 Directors cut DVD version. (00:49:02)
Visible crew/equipment: When Roger is talking to the guy next to him at the start of the film the guy gets shot and for a brief second you can see a fake blood packet covered by make up.
Revealing mistake: When Stephen is trying to climb out the elevator after having been shot, a group of zombies attack him and the first zombie we see bites his leg. In this closeup of Stephen's leg being bitten, the tube that pumps out the blood is protruding out his trousers, obviously leading up his thigh.
Visible crew/equipment: During the ghetto holocaust at the beginning, when Willie kicks open the last door (before Peter kills him) you can see the camera's shadow on the door as it swings open.
Revealing mistake: When Peter shoots the biker out the sidecar there is already blood on the ground before he lands.
Revealing mistake: A zombie's make-up is smeared when Stephen is fighting with it on the grass at the refueling scene. Stephen is pushing the zombie's head back and the make-up on his forehead is wiped off.
Continuity mistake: When Peter and Roger enter the Penney's store, Peter throws his M16 and the keys inside the store before he starts to close the door, yet Peter's rifle (Roger is holding his M16) can be seen propped against the wall outside the door twice in the following shots.
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.