Continuity mistake: When Carrie-Anne Moss leaves the house to bring drinks to her son and Fido, she closes the red front door behind her. When we cut to Fido's POV of her approaching, the door is wide open.
Revealing mistake: In a scene where Fido is turned around, you can see a part of his head that is pink. However the rest of his body is grey.
Other mistake: When Helen kills the zombie bully she fires 9 shots from a 6 shot revolver.