The version that I rented (when looking for a humorously bad movie, mind you) had the gall to put Don Knotts on the cover of the box. What a joke. A disembodied Knotts provides the voice for a mule that occasionally appears during the movie, voicing perhaps 15 lines - a solid half hour of work for old Don. The rest of the movie is beyond incomprehensible - film quality that is beyond terrible, jump cuts everywhere, horrible sound, and no discernable story or point. Was it intended to be a comedy? The (near) presence of Don Knotts would seem to indicate that, but the dreary pacing and tone of the film suggests that Stanley Kubrick directed the film while hung over.
So while I had hoped to find something that could be ironically enjoyable, the experience of watching Mule Feathers just felt like being beaten mercilessly in the head with a board.