Nate's wardrobe in the film's finale changes from white to black depending on whether he's inside or outside (caused by filming outside scenes with infra-red lights).
Nick is referred to as Jim's roommate by Pete in the beginning of the film, yet later Amy talks of Nick and Jim's roommate as separate people.
Prior to Nate's fantasy sequence in the park, his hand switches places as he puts it to his forehead.
When Jim answers Amy's phone call, his pants turn into shorts.
Tripod visible when Nate sits on the ground looking at pictures.