In 1990, I went to see the sequel to The Neverending Story--I never understood what was going on, other than a witch stole memories at some point and stuck them into some sort of orb.

And I never knew it was based on a book until less than a week ago, when I read about it at Wikipedia.

Oh, and I was wrong--I watched 15 minutes of Labyrinth in middle school, found it boring, and turned it off.