It's a movie my sister and I thought was hilarious--The Possession. There's a terrific scene where they give the possessed girl an MRI and see a little demon in there making faces at them.

Although one thing we did learn is that apparently radiologists don't see gorillas when they are superimposed on MRIs. It was some experiment done to see if they'd notice that while looking for cancer or something. Most of the radiologists in the study reported all sorts of findings but failed to see the gorilla. Because really, who is looking for a gorilla on an MRI?