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: When Harrigan is watching the surveillance video by Bill Paxton he states that the helicopter is a silver Alouette when it is actually an AS-350.
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.
Character mistake: When Chafuka is controlling the zombie Barry with her voodoo doll, he's supposed to be repeating her words so precisely that he even imitates her accent. But when she says "that darn fool paper, it fall on the ground," Barry repeats it as "The darn fool paper fell down to the ground."