What Could Have Been: Carrey was originally supposed to be a cast member on Saturday Night Live when the original cast left in 1980 and Jean Doumanian was hired to create a new "Not Ready for Primetime" cast for the sixth season. Considering how terrible the 1980-1981 season was and how most of the cast has faded into obscurity (with Eddie Murphy, Gilbert Gottfried, and Gail Matthius [when she spent most of the 1990s doing voicework on kids' cartoons], as the only ones who found fame outside of their time on SNL), it was probably a good thing he wasn't picked.
Plus, the Wachowski Brothers wanted him to play Plastic Man in the never-made film based on their script. Which, even if the script was kinda crappy, still would have been epic.
He almost didn't do Ace Ventura because he didn't care for the script. He only said yes after they allowed him to work on it.