"Lights, camera, and anguish!"

REASONS:
1. Written, edited, starring AND directed by......the special effects man.
2. A movie within a movie about making a movie!
3. The villain's office number is 666, I kid you not.

Full movie available free to watch on Internet Archive, because the writer/sfx-guy/star/director believes if more people saw his work, he would at last be truly appreciated:
https://archive.org/details/wizard-of-speed-and-time-bearded-swordsman-ver-1

In 1979, Mike Jittlov, a special-effects man, made a short stop-motion film starring himself. Years later, he decided to do a full-length semi-musical sort-of-comedy feature film, also starring himself, about the dramatic making of the short film (Wiki generously refers to it as a "(semi-)fictionalized account". Not sure if it's a comedy or a biting look at the overly-unionized industries of Hollywood and in every way a passion project to showcase special effects processes with a plot loosely revolving around a group of non-actors pretending to be actors, this is a hokey nightmare, but you know what? It's also a legitimately enjoyable trip. This is something I first saw when I was about 4, and there were scenes that stuck with me for decades until I found out what it was.