Revealing mistake: Just before the truck slides off the cliff edge, you can see that the truck's cab door is open where the stunt driver jumped out.
Revealing mistake: When the bats invade Dr. Dunwoody's bedroom, you can see the strings on one of them.
Revealing mistake: Near the end the psycho killer pays a black man to beat him up so that he can then blame the injuries on Dirty Harry. Watch the killer's hairdo as he gets punched and beaten: a couple of rear-view scenes show an obviously fake wig, intended to look like the killer's own bad-hair-day style. (01:16:05)
Revealing mistake: When the doctors first arrive by helicopter in the town, they're looking around. The Minister lying upside down on the stairs moves his eyes and forehead as if looking to see what's going on, on the set. (00:22:15)