Character mistake: When Kevin is shooting the toys off the laundry chute with Buzz's BB gun, he's looking through the scope with his closed eye.
Character mistake: When the Grand High Witch and her assistant enter her room while Luke gets the formula, they're wearing pointy shoes. Earlier, it was mentioned that witches never wear pointy shoes.
Character mistake: The spelling of Koreander/Coriander's name varies between the opening credits (spelled with a C), the shop window (spelled with a K), the inner cover of the book (spelled with a K) and the book's text (spelled with a C).
Character mistake: At the ravine, upon learning that the bridge doesn't exist yet, Marty states to Doc "We can't wait a year and a half for this to be built". If you carefully look at the sign, it says the bridge is opening Summer 1886. That's under a year away, not a year and a half from Sept. 1885.
Character mistake: Big Ben is loaded feet first into the ambulance, he should've been loaded head first.
Character mistake: When Raphael is chasing Casey Jones after their fight he vaults over a taxi hood, never takes his eyes off Casey, but he somehow loses him.
Suggested correction: 2 things are happening; a shell backed stocky Raphael is chasing a lighter human athlete Casey. Casey has freedom of movement, whereas Raphael can't stray much from the shadows in hiding. :-) A knocked out Casey wouldn't be helping the Turtles out of the next evening with that memorable entry so I'm glad Raph lost the chase.