Continuity mistake: The zombie baby keeps changing size throughout the movie.
Factual error: As the Thug Zombie is on top of the lawnmower and is getting hacked to bits, his body parts don't fly off. His arms would've gone everywhere when the blade reached his shoulders, and the same goes for his head. (01:29:15)
Continuity mistake: When Lionel's mum gets bitten at the zoo, the colour of her sleeve material changes from black/dark blue to light blue. (00:17:45)
Continuity mistake: Despite being absolutely drenched with blood during the zombie massacre, Lionel's sweater and pants are completely dry in all the following scenes. His pants are amazingly clean, too. (01:25:45 - 01:32:00)
Revealing mistake: As the three zombies go rabid at the house party, and McGruder and Thug tear the skin off a guy's face, the switch from actor to dummy is visible. (01:10:55)
Continuity mistake: Just after the Kung-Fu Priest scene, and Lionel is feeding the zombies tranquilized porridge, Nurse McTevish swallows some and it pours out of her throat. After Lionel has put it into the nurses throat, the porridge has disappeared.
Other mistake: As Lionel is hanging from the ceiling and the zombie priest and nurse come toward each other, the pitchfork that Uncle Lez shoved into the priest impales the nurse and it is covered with blood. A split second later it is clean. (01:22:45)
Revealing mistake: When the Thug Zombie has been torn in half and it is crawling toward Lionel, you can see the shadow of the actor's body being dragged behind it. (01:16:05)
Visible crew/equipment: When Lionel has locked himself in the bathroom the thug zombie breaks through the door and is ripped in half, and you can see the hole in the floor for the actor's body. (01:16:00)
Continuity mistake: When Paquita is trying to get Rita back on her feet, and the top of that zombie's head slides toward them, Paquita kicks it. It flips onto its side, but the next shot has it sliding right way up again. (01:25:25)
Continuity mistake: In one scene Lionel is cleaning bloody footprints off the floor. Then Paquita comes round, and Vera eats her dog. Then Vera attacks Lionel, and they roll down the stairs. As they roll down the stairs you can see the footprints are now different from before. (00:28:10 - 00:29:45)
Other mistake: When Lionel has been dragged back up to the ceiling by Thug Zombie's guts, chews the intestine, falls back down and collides with a zombies head, he doesn't really make any contact with it and yet it STILL explodes... (01:22:35)
Other mistake: Towards the end when the top half of the zombie thug is on the lawnmower blades, you can see the jets of 'blood' being sprayed up at different angles. (01:29:20)