Sir Ringo Starr and Barbara Bach began their long relationship after meeting on the set of this movie. They were married ten months after they met.
This movie opens up with "One Zillion B.C. - October 9th". The date of October 9th was John Lennon's birthday. This was in memory of Sir Ringo Starr's friend and former bandmate with The Beatles.
In an interview, Shelley Long said that at her audition, she didn't speak any English. She responded to everything with an ad-libbed series of grunts. It obviously worked.
The following Cavespeak from the movie translates as follows: "alunda" - love; "bobo" - friend; "haraka" - fire; "macha" - monster; "nya" - no/not; "ool" - food; "pooka" - broken; "ugh" - like; "kooda" - come/follow; "zug zug" - have sex; "fecchh" - "shit"/general profanity.
Before she met Sir Ringo Starr and the two fell in love, Barbara Bach is on record as saying that she was originally disappointed that the lead part had gone to him instead of "a top comedian like Dudley Moore".
When showing at the old drive-in theaters in Australia every ticket holder was given a pamphlet with approximately thirty "caveman words" and an English translation for each word to listen for through the movie.
This movie was released the same year as a serious "caveman" movie, Quest for Fire (1981), as well as Mel Brooks' History of the World: Part I (1981), which had its own comic caveman sequence.
Jim Danforth, special effects designer of the stop-motion animated dinosaurs (the dinosaur and effects designer), apparently left the production of this movie about two-thirds of the way through because the Directors Guild of America allegedly disallowed his already contracted co-director credit alongside director Carl Gottlieb. Therefore, Danforth is not credited as a director on this movie, only for special effects and second unit director.