Crossover
In the final episode "The Aceman Cometh" the Mask teamed up with Ace Ventura, another Jim Carrey movie character. At the time of the original airing Ace Ventura: Pet Detective was running in the adjoining time slot in CBS's Saturday morning lineup. During the crossover Stanley/Mask and Ace keep their own respective animation style while within the other's show.
Milo, Stanley's dog, has his brain switched with that of a scientist and is then dognapped. Stanley in turn hires Ace Ventura to help get him back. Upon the end of the episode, Spike, Ace's pet monkey, steals the mask. Stanley travels to Florida to get the mask back. The crossover is concluded in the Ace Ventura: Pet Detective episode "Have Mask, Will Travel".
Read more about this topic: The Mask: The Animated Series