When the main character is walking through his studio, you can see a half done painting, by one of his students. When he walks by the same painting, in the same scene, you can see that the painting is now fully done.
O.k> first of all my father wrote this"cheesy" movie! I don't think it was considered "cheesy" at the time! In fact its become a semi-cultist film!
second, I dont believe the painting was left that way by mistake, I believe that the muse "Kira"(Olivia Newton John) did it! That was part of the story!
sincerely, Kira, the daughter of the writer.