Continuity mistake: In the Pacific Playland scene, Wichita and Little Rock are seen riding a Swinging Ship when all of a sudden, zombies begin to pile over the park's fence. In the next scene, the two girls are shown running down a stretch of walkway shooting at the zombies that are chasing them. When the camera is focused on the zombies pursuing the girls, in the background (top left corner) you can see the Ship ride sitting still. After the camera gets a shot of the girls, it goes back to the shot of the zombies and the Ship is now moving in full swing. The next time the zombies are shown, the Ship is sitting still again. There was no time between shots for the ride to have started and stopped so quickly.
Continuity mistake: In the scene after Wichita and Little Rock stole Tallahassee's SUV, we see a huge shot of the camera panning downward as Columbus is talking to Tallahassee. We get to see a clear shot of the sky, which is very cloudy and no visible sun. As the camera moves with the two as they continue off screen, the next shot is from directly in front of them walking forward. However this time the sun is glaring brightly behind them leaving shadows from the buildings and lighting the road up with the bright sun. But in the shot before it was a very cloudy day.
Continuity mistake: When Columbus and Tallahassee first meet, they are sitting in the car and Tallahassee picks up his bottle of 'alcohol'. The label on the bottle changes sides depending on camera angle. From Columbus' side the label is facing toward the front of the car (with Tallahassee's fingers over it), but from Tallahassee's side the label is facing towards the driver's window. It then changes back and forth depending on camera angle.
Continuity mistake: Woody Harrelson locks himself in the booth at Pacific Playland and locks/closes the security screens on three sides. After he is surrounded by zombies, one of the side cages has been pushed opened a bit, leaving quite a gap. The scene pans around to various angles as Woody fires away, and in a subsequent shot, the screen is shut again. With both his hands full, he couldn't have shut it.
Factual error: During action sequences in the amusement park the girls attempt to escape in their Hummer, and a zombie head-butts the passenger window, causing it to shatter. As has been demonstrated on numerous occasions, including a Mythbusters program, tempered automotive glass will not break when struck by a blunt object and that would include a zombie's head. Only a blow from a sharply pointed object will break tempered glass.
Other mistake: When Columbus is face-to-face with the clown zombie, he looks up at Wichita, who is on the ride, stuck at the top of the tower. Columbus looks almost straight up at her, but when Wichita looks to Columbus for help, she should look almost straight down, but instead she looks straight ahead. There is no other reason why she would have looked straight ahead because a) Columbus was directly below her, b) Little Rock and Tallahassee were to her right, and c) she almost perpetually had her eyes on the zombie climbing the tower towards her.