Before Jim Carrey landed the lead role and made it his own, 1994's Ace Ventura: Pet Detective almost starred several other surprising actors. Carrey's first big film success story, Ace Ventura feels like a character and project so tailor made for the actor and comedian that it's almost impossible to imagine anyone else playing the part. That's actually somewhat true, as once he came aboard, Carrey helped rewrite the script, and came up with Ace's voice and behaviors himself, some of which were inspired by his prior stand-up comedy characters.
However, Ace Ventura: Pet Detective existed as a potential film project long before Carrey was cast. The concept wasn't invented for the then In Living Color star, and production studio Morgan Creek, along with co-writer/director Tom Shadyac, considered multiple other performers for the Ace Ventura role before he was cast. If Avengers: Endgame's time travel rules are true, somewhere in the multiverse there are places where these people did indeed get cast, leading to bizarre alternate versions of the film we know.
Would Ace Ventura have succeeded if played by anyone besides Carrey? Probably not in his final form, but perhaps if the character had been written differently. And it probably would've been, as it's hard to imagine any of the following actors talking out of their butt onscreen.
The Actors Who Almost Played Ace Ventura (Instead of Jim Carrey)
Surprisingly enough, 1980s comedy star Rick Moranis was the first choice to play Ace Ventura, to the point that the film's producers actually offered him the role. Moranis, best known for films like Ghostbusters and Spaceballs, turned them down, however. It's unclear why, as he was still active in Hollywood at that point. Perhaps he just couldn't envision himself as the titular pet detective. After Moranis said no, producers then considered both The Breakfast Club's Judd Nelson and Die Hard's Alan Rickman for the lead.
Both seem like really odd choices, as Nelson and Rickman are both best known for dramatic roles, although they have shown comedy chops from time to time. If either had taken the part, one assumes Ace Ventura would've been a more droll, sardonic quipster, as opposed to the animated physical presence Jim Carrey played him as. In the weirdest turn of events, producers also considered making it Alice Ventura: Pet Detective, and casting Whoopi Goldberg in the part. It's unclear why they decided not to do that, but one wonders if Goldberg would've taken the gig if it had been offered. While an Oscar-winner by then, she definitely made some really odd decisions in the 1990s. Thankfully, producers saw Carrey on In Living Color, and the Ace Ventura: Pet Detective we know was born.