The famous "With this axe, I rule!" line at the end of the movie is actually the title of a Robert E. Howard short story about Kull, which was rejected by Howard's then primary publisher, "Weird Tales" magazine. He later rewrote and sold the story as "The Phoenix on the Sword", the first Conan story, which makes the item that this project was initially developed to be a "Conan" film somewhat ironic.
In the Finnish translations of the Kull stories, the character name 'Kull' was changed into 'Kall' to avoid unintentional comic elements (there is a Finnish word meaning 'penis' that resembles 'kull' quite a bit). This, however, was not done with this movie, adding its part to the unintentional comedy.
The trivia item below may give away important plot points.
The dead man from whom Kull takes the axe in the cave of the god was supposed to be Kull's father, but this idea was scrapped before the film was actually shot (although it remains in the movie's novelization).