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).
Visible crew/equipment: When 3 of the zombies are high on Animal Stimulants and are going rabid at the house party, several girls have locked themselves in a room. A guy starts to crawl in with no flesh from his waist down. In one of the shots as they pull him in, you can see his REAL body as the skinless legs are kicking (Look for a pair of black pants).