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The actors playing the parents both previously appeared in films with a similar theme of suspended animation and revival. Mariette Hartley appeared in Genesis II (1973), about a man in suspended animation revived in the distant future after being buried by an earthquake; and Richard Masur appeared in The Thing (1982), as part of a team of scientists who revive a frozen, buried alien from the past. Hartley Also appeared in All Our Yesterdays (1969) as a woman teleported back to the ice age of a planet about to be destroyed by a supernova.
Originally, the filmmakers offered the role of Link to Pauly Shore. When Shore first went in to meet with Disney chairman Jeffrey Katzenberg, he told him he didn't want to play Link. Because he knew, since cavemen don't talk, that the film would lose the appeal of his humor and unique "Paulyspeak", (where Shore would pause between syllables of key adjectives). Instead, Shore wanted to play one of the two teens who find the caveman. So, Katzenberg insisted that Shore, along with the writers, re-write Harold (the character's original name) to become the Stoney Brown character. Shore improvised most of his lines.
At 6'3", Brendan Fraser was actually too big for the clothing that costume designer Marie France had originally purchased for him. Since Fraser's outfits were supposed to look baggy on him, France had to specially make all of them.
In the scene where Brendan Fraser is eating out of the dog bowl, he is actually eating Cookie Crisp.
Ke Huy Quan and Sean Astin appeared on-screen together briefly in this movie. It marks the first and only time any original cast members of The Goonies (1985) appeared on screen together again.
For the scene where Link is in the bath, Brendan Fraser was popping real bath beads into his mouth. He had a bucket nearby to spit them into after each take.