Revealing mistake: When The Mask dances with Tina for the first time, after he swings her around the floor you can see the stunt double's face, older than Cameron Diaz.
Continuity mistake: When The Mask paints the flush handle, near the end of the movie, watch the far left hand side when it shows Tina and The Mask. The Mask is shutting a door on the tree where the flush handle really is.
Visible crew/equipment: Towards the end of the film you see the long haired baddie grab Milo by the hind legs (just before Milo puts the mask on). As Milo starts to change you can just about see the baddie who is holding his legs, except he is now a different person with brown curly hair, nobody who is seen prior or following this shot. Presumably he is the dog trainer. (01:23:15)
Continuity mistake: When The Mask escapes the club shootout, Dorian is left shooting at the air. He then gets tired and put his gun down. When the police arrive, he somehow has his gun raised again.
Continuity mistake: When Tina kicks the mask out of Dorian's hand and Milo leaps through the air to catch it, he catches it with his mouth at the mask's chin, yet when he lands the mask has been turned round so the chin end is now facing the ground. (01:22:45)
Continuity mistake: In the very beginning, when the scuba diver is trying to open the chest and gets hit with the pipe, at first the pipe is held by a rope near the middle and when it's lowered into the water it is held by a chain at each end. After it hits the guy and is let go from the chains they are wrapped around three times. (00:01:00)
Continuity mistake: When Stanley is beating up Dorian, Dorian's head is either lying against the ground or raised, depending on the shot. (01:27:49)
Chosen answer: It's an old car, so obviously a numbr of things could be wrong with it, like the clutch or the engine. Faults with either of these things would cause a car to brake in this way.