Milo is dognapped and having seen a TV commercial, Stanley calls in Ace Ventura to help. Ace discovers Stanley's secret and the duo join forces. Exit sanity.
Quite a clever gimmick really having the animated versions of two characters originally played by Jim Carrey appearing together in the in the same cartoon. (Unfortunately, the animation of Ace doesn't quite blend in with the cartoon world of The Mask.) You might think it ends there but it's actually a two-part crossover continuing in the Ace Ventura episode "Have Mask, Will Travel".
NB Some episodes of this show maybe streaming at the following locations
