At the climax of the episode when lightning strikes Cthulhu, Alice is thrown against Peter by the blast. Her position changes from face down to back down and then back again from shot to shot.
Before the police arrive at the end, Ray's uniform is colored incorrectly.
When Ray pulls the copy of Weird Tales from his belt the title is misspelled "wierd".
When Winston breaks free from the stone, his trap is drawn on the wrong side.