Revealing mistake: When Irene trips by the cliff she just kicks the floor and twists her ankle.
Visible crew/equipment: When Charlie starts beating the mirror on the train you can see the boom mic on the right of the reflection.
Continuity mistake: Irene's hair moves back and forth between behind and in front of her right shoulder in the scene where she tells the police officer about her accident. It undergoes further changes when she talks to Dickie on the phone. (00:24:45)
Visible crew/equipment: At the end of the introduction with the cruising Charlie there is a crew reflection in the windbreaker. (00:01:50)
Factual error: After Jim Carrey has his first "episode", the police car pulls up to the officer in charge, and it has blue lights on both sides. In Rhode Island, all police cars must have red lights only. (00:22:00)
Continuity mistake: In the scene where Charlie shoots the cow, no flame or smoke is seen coming from the gun in some shots, but all the others show flames and/or smoke. (00:30:50)
Continuity mistake: In the scene where the three Baileygates brother's are in a field with tents etc, helping the police to track down their father, Lee Harvey is wearing a plain grey vest. In alternating shots the vest changes to one with black edging, and then back to plain grey again. (00:47:30 - 00:48:40)
Revealing mistake: When Hank crashes the car through the shop, look at the barber's chair. You can see it's a stunt double for the actor.
Continuity mistake: When Dickie is in Hank's and Irene's train cabin, Irene hits him over the head and he lands on top of Hank. You can see his head is behind Hanks shoulder, but when Hank wakes up Dicky's head is next to Hanks. (01:25:45)
Continuity mistake: After Hank has conned Irene into sleeping with him, the morning after Irene finds the "Coke" machine smashed up. In a later scene the Coke machine is back in perfect condition.
Character mistake: Throughout the movie, Carrey's Commanding Officer, who is a Colonel, is called Captain.
Other mistake: When the cow is seen on the road, note the black and white patterning on its hide. At the end, when you see the cow in a neck brace, it has different patterning. (00:29:50 - 01:44:35)
Continuity mistake: The bandage on Jim Carrey's chin changes size frequently throughout the movie.
Visible crew/equipment: When Charlie talks to the little girl with the rope, the mic and two hands holding it are reflected in the helmet. (00:17:55)
Continuity mistake: When Charlie/Hank and Irene arrive at the train station in Rhode Island. Charlie and Hank are having a "fight", during this fight Hank unzips his pants to wiggle his "thing" at a group of ladies sitting on a bench. Immediately after that he falls to the ground and his pants are zipped. (01:28:40)
Continuity mistake: In the scene where Charlie is being chased through the train station and gets shot in the arm look out for a boy in the train station with a green top because immediately after he exits the station the boy is sitting on a bench outside. (01:29:45)
Chosen answer: If you watch until after the end credits, you see it get eaten by a fish.
J I Cohen