Revealing mistake: At the beginning, when the grandma zombie knocks off that guys head, a geyser of blood pours out. When the body falls forward and the blood splatters the camera, the body lifts up about three centimetres before it falls down, indicating that it is a dummy.
Revealing mistake: During the first flashback of the (hilarious) zombie fish, there are several shots of the raincloud above Marion. They are exactly the same as one of the pre-credit clouds.