Continuity mistake: When the top of the zombie's head slides toward Rita, the floor around it is clean. As soon as the shot changes, there's blood all around it, and then it changes again, when Paquita kicks it. (01:25:20)
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: 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)
Visible crew/equipment: After the uncle has been torn apart by the mother, he goes after Pequita and you can see the wire holding his head up. (01:27:50)
Revealing mistake: When Lionel has just finished massacring the zombies, Thug Zombie appears at the top of the stairs. If you look closely you can see his real pair of legs near the window Lionel flew out of earlier. (01:28:35)
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)
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)
Continuity mistake: After Lionel is swallowed by his mother's stomach, he is absolutely covered in blood and intestines, but in the next shot, when he's helping Paquita, he's nearly clean. (01:34:50)
Continuity mistake: The zombie baby keeps changing size throughout the movie.
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.
Continuity mistake: During the scene in which Lionel is in the basement attempting to sedate the nurse and his mother, he is startled by a falling crockery. After the rat runs past him, the nurse attacks him. He stabs her in the nose with the syringe, however, the following shots show the syringe is embedded in her eye.
Revealing mistake: When Paquita discovers the zombies tied up in the basement and convinces Lionel to kill them, he gets the "poison" and injects them with it. Look closely: the shelf that he gets it off is the same as the VETS' shelf in a much earlier scene (Even the bottle of tranquilizer that Lionel dropped is back there).
Plot hole: After Lionel locks zombie mum and the nurse in the basement, he tells his girlfriend that the went to the hospital in the nurse's car and she leaves, but wouldn't she notice that the car is still there?