Here's one of the biggest and widely popularized theories about this film: the classic Pink Floyd album 'Dark Side of the Moon' was deliberately written to be played in time with 'The Wizard of Oz', or specifically, that if you start the movie and the album at exactly the same time, with the sound on the movie switched off, events on the movie synchronize with sounds and themes on the album. The tornado, for example, is supposed to line up perfectly with the screaming on the track 'The Great Gig in the Sky'.
Everybody who has ever been involved in making that Pink Floyd record, and has been willing to talk about it, has said that there's no truth to it at all. 'Dark Side of the Moon' was made in 1973, where the technology required to freeze frame and synchronize the movie to the music so precisely just wasn't available.