Revealing mistake: When Shrek and Donkey are sitting by the fire and looking at the stars, when Donkey asks Shrek about "our swamp" and Shrek says "We?" When Shrek blinks, his right eyeball is slicing through his upper lid. (00:46:30)
Revealing mistake: When the monsters approach The Cyber gang outside the arcade, Cyber Scooby (who wears the red color) is seen in a blue color in one of the shots facing the arcade.
Revealing mistake: When Professor Oak is getting a book from a bookshelf, the book appears out of nowhere. (01:15:52)