Revealing mistakes: When the tingler attacks the sedated Dr. Chapin, you can see the wire that is pulling it.
Continuity: When the tingler is breaking out of the cage you can see a wire at the bottom pulling it open.
Incorrectly regarded as goofs: Hair and nails do not continue to grow after one dies, as Dr. Chapin asserts. The illusion of growth is created by the shrinkage of the flesh surrounding the hair and nails. However, the belief in growth after death has become so ingrained in common folklore that it is not surprising to see it used as "fact" in a horror film; such films play on our fears and knowledge of folklore to achieve their effects.
Continuity: The title on the book that Warren is reading as he is waiting for Isabel to come home from her date is on the back cover instead of the front cover.
Continuity: When Price does autopsy on Ollie's wife he tucks up his sleeves and wears gloves. The shot after shows his sleeves are down again, and then up again in a different way in the next shot.