Now bout the movie. The two leads just act in a wonderful way. Especially Kevin Spacey. I also liked the plot a lot. There's enough evidence pro and contra that Prot is from K-PAX, or is not. I don't want to say too much bout the film, just watch it if you haven't yet.
But I want to write my own humble opinion bout whether Prot is or is not frm K-PAX. I believe he is. Because Bess just disappeared and because he can see UV rays and knows the things bout space etc. The evidence they give you bout this Robert Porter could be something else. I mean this is just human and could be another human. But all the stuff that is inhuman can't be just put aside. Then why is his body left there? Now this may sound odd to you, but it is clear to me: when he entered planet Earth he needed a Earth-body. So one was 'created' and he lived in it. So when he leaves he doesn't need it anymore and the corpse, the mortal frame, is left behing with some sort of life in it, the life that is connected to the body and not to the soul. Then why isn't Bess's body left behind? Her true 'body' is the Earth one. So she takes it with her, then gets an own body on K-PAX which she will leave behind when going back to Earth. But Prot left nothing behind on K-PAX. Maybe my theory is confusing. But you just need to have one body, don't you? And you can't have 2 nor can you keep the second one nor can you just destroy it. It may also be that Prot just got the body from Robert Porter, because this one died and thus didn't need his body anymore. They never found the corpse anyway. He may just have arrived on Earth on the very day Robert Porter died (what actually IS true) and then have gotten this corpse.
Hm... of course there are weak points in my theory and you could find arguments against it. But there is no 'true' one, and I believe in mine.