In the very last minute of Paranormal Activity 4, (I'm not even joking. This is like the very few SECONDS of the entire movie before the credits.) when Alex is in the room of the abandoned house where she suddenly stops dead in her tracks to see a posessed Katie across the hallway, there is a slip-up. When Katie starts storming after Alex, watch this part frame-by-frame. There's two mishaps in this part that even I didn't catch in the first viewing until someone posted a video about this. When you hit the frame just as Alex slams the door on Katie, the next frame cuts to partially the ceiling of the room. Then it just continues on where Katie is shown with her uppermost part of her body through the door and the scene progresses.

Also, if you notice Katie's shirt as she starts running, it's black. But when it shows her struggling through the door, it's white.

If anyone else has noticed this particular slip-up or any other slip-up in this film, please let me know in the comments or add your own slip-up on here.

Thanks! :)

David