The original cut of the film included clips from training films for surgeons for shock value. After initial showings, these were trimmed down, hence the short running time.
On its first release, the original version was allegedly banned by several theatres across the US, so it was then edited. No prints of the unedited version are known to exist.
Acquired by Ted V. Mikels for release as part of a triple feature with The Corpse Grinders (1971) and The Embalmer (1965). It was Mikels who cut out most of the "gore" scenes and a sequence with Ray Dannis in drag. This shortened the film from a reported 80 minutes to its subsequent length of just over an hour.
Lines from a trailer for The Undertaker and His Pals were sampled by recording artist Rob Zombie for his song "What Lurks On Channel X".
Harry's car is a 1965 Buick Wildcat convertible.