This may be apocryphal, but I heard that "I am the Walrus" was written in reaction to some fan mail John received. Some British schoolkids (from Liverpool!) commented how much they enjoyed analyzing Beatles songs in English class. John was so amused that anyone would take Beatles songs that seriously that he penned "I am the Walrus" as something so weird that it would defy any analysis!!!

Editing to add that the movie, "Magical Mystery Tour" is just plain disturbing. Even friends of mine who were high while watching it thought it was freaky!