When Marge gets her first assignment as a police officer, chief Wiggum says her beat is Junkyville and Bumtown. In the next scene Marge is seen walking in front of Junkytown legal clinic.
In Act 1, from when Homer plays 3 Card Monty till when Marge hits the dealer over the head with a garbage bin lid, Marge's necklace is white instead of the usual red.
When Marge is doing the police car course to earn her police badge, she is wearing a white shirt and her hair is in her signature tall style. When she finishes the course, she is wearing her police uniform and her hat is on with her hair down.
When Homer walks in on the crime ring in the garage, he leaves the door open. When he attempts to exit the garage, the door has magically closed.
When Herman is being arrested at the end of the episode Chief Wiggum's hair is black instead of the usual blue.
The animation of Marge de-cocking her service revolver (at the beauty salon) is wrong. Her 2nd hand never moves and yet, we hear the gun de-cocking when she realizes there was no threat. In reality, you need to keep your firing finger on the trigger (which she does) but also put your other hand on the hammer - ideally, in front of the firing pin, to prevent it from going off.
While on the shooting range, Marge fires 24 rounds from her pistol without changing the magazine.
The family station wagon has a baby blue paint job when Marge parks it in the garage right before she rolls out the door as it begins to lower. It should be a reddish orange.