I used to think the most bizarre Disney film was THE STORY OF MENSTRUATION. That was, until I saw VD ATTACK PLAN (1973), an educational short about that most Disney of subjects: venereal diseases. The film was directed by Nine Old Man, Les Clark, and animated by Charlie Downs, who manages to create some really interesting movement for a main character who has no arms or legs. Here's a short article about the film. And you can watch the film below, in its entirety, courtesy of Google Video:
(Thanks, Benjamin Plouffe)