- Follow the Leader: The Fifth Element borrows heavily from the Harry Canyon segment.
- Recursive Adaptation: Den started as an animated short before it was a comic.
- Suspiciously Similar Song: Elmer Bernstein reworked some of his Heavy Metal score as "Dana's Theme" from Ghostbusters (1984).
- What Could Have Been:
- The plot was meant to be connected and more complex than an anthology, but due to the release date being bumped up and a rushed production, the animation had to be done by several animation houses, including CinéGroup and Atkinson Film-Arts. Some of the ideas were Hanover Fiste showing up in So Beautiful, So Dangerous, appearing on Zeke and Edsel's ship, saying "Sternn will go free!" and a sequence linking Sternn and B-17 called Neverwhereland, wherein the Loc-Nar lands on a planet and affecting its development.
- Kyle Gass had revealed that the director of Kung Fu Panda had approached Tenacious D with an idea for a remake of Heavy Metal. The band was to appear in it as a duo of alien stoners, and they even composed the song "Deth Starr" for the film. Unfortunately, though, the idea never came to pass for fear that an R-rated cartoon would not sell well, so the band ended up releasing the song years later on their album Rize of the Fenix.
- Along with Tenacious D, David Fincher was also planning to do a segment for the film with Tim Miller. That eventually spun off to Love, Death & Robots, 11 years later.
Trivia / Heavy Metal