Revealing mistake: May's zombie is breathing before it is brought to life by her, when she puts the cigarette packet in its pocket you can see it's chest rise and it's neck pulsate. (01:19:20)
Factual error: When May cuts her eye out with the scissors at the end of the movie, the fake eyeball used for the effect is perfectly round. A human eyeball is far from being perfectly round.
Revealing mistake: In the scene where May is visiting Polly's house after she overhears Adam's true feelings, she is playing with the pack of cigarettes that Adam gave her. There is a symbol of a camel located right below the filter of the cigarette, meaning that the cigarettes are Camels. Yet the brand is a generic one.
