I saw K-Pax last night and my friend Simon dared me to put the K-PAX poster, I took from the theatre, up on eBay. Here's the K-PAX poster on eBay. I told him that people will buy anything on eBay.
After coming home from the movie I had to read all the K-PAX reviews to see if I understood the ending.
[Stop reading here if you don't want to know the ending]
None of the reviewers actually comes out and describes the meaning of the ending. I guess that's good, because I hate it when a movie reviewer gives away the end of a movie.
[Really... I mean it, stop reading here if you don't want to know the ending]
Roger Ebert comes close when he says, "perhaps Prot simply borrowed a human form."
I think that Prot came down to earth and borrowed Proctor's body after Proctor jumped into the water. At that point, Prot used the body to tour the planet. Prot was swinging Jeff Bridges daughter with the other guy's deeper memories. At the end, when Prot jumped on a beam of light and left, Proctor was left having to deal with seven lost years and the trauma of what happend at the cabin.