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: 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.