Two teenage airheads, Dak and Eddie, get radioactive so they can get powers. Meanwhile, Lt. Mitch Kellaway is sure Stanley Ipkiss is The Mask and handcuffs himself to Stanley to prove it.
Pretorius sets in motion his latest creation - a sister Mask that has to turn the real Mask into a living puppet and then use him to steal meteorite fragments with unusual properties.
Stanley finally becomes romantically involved with a shy, awkward customer. She accidentally finds and puts on his mask and the results are she becomes a loud, man-hungry woman. In the mean time Pretorius is looking for a female companion.
Stanley succeeds into removing the power of the mask, which enables him to act like the goofy character on his own. But he has to get the powerless Mask to work again when Kablamus arrives in Edge City.
Stanley gets rid of the mask by handing it to his therapist Dr. Neuman. All hell breaks loose when the therapist puts the mask on and joins forces with Pretorius.
According to Stanley, Mayor Tilton has to be taught a lesson how to run the Edge City better. So Stanley puts on the Mask and starts a campaign to become the new mayor. Soon it comes to light that Mayor Tilton is kidnapped and Pretorius is masquerading as him so he can turn all of Edge City into subjects for toxic waste experiments.
Milo wears the Mask to spoil the sinister plan of a mad dogcatcher named Willamina Bubask. Stanley is being stalked by Walter at Cheap Chucky's Chili Cook-Off.
It's Halloween and Skillit manages to escape from reform school. Skillit seeks revenge on the Mask and uses the help of Atilla the Hun, Billy the Kid and an evil Merlin.
The Mask breaks in half during Walter's attempt to retrieve it. Now both Stanley and the Mask are existing at the same time. Chet Bozzack, an old high school bully of Stanley, gets and puts on the other half of the mask.