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: A newspaper is shown saying "Girls Body Found" as plural when it should be "Girl's Body Found" as a possessive.
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: Big Ben is loaded feet first into the ambulance, he should've been loaded head first.
Character mistake: Given Billy still remembered and recognized him it seems strange Kate doesn't when she mistakes Daffy for Gizmo.
Suggested correction: Billy spent significantly more time bonding with Gizmo in the first movie - days and days. By contrast Kate had very little actual time with him.