Revealing mistake: In the scene where Rudolph is saving Tony from the truck he says, "close your eyes, Tony". But in the next scene when they are on the blimp the boys introduce themselves. Rudolph did not yet know Tony's name but yet he said it.
Continuity mistake: When Tony is in the lesson talking about vampires, the blackboard behind the teacher is free of any writing. Then, between shots, '300' is written on the blackboard, even though the teacher didn't write it.
Audio problem: When Tony goes down to help Rudoplh after he tries to fly out of the window, Tony asks him if he's okay and you can hear Rudoplh saying "Do I look it?" but his lips never move.
Audio problem: When Tony says, "It was," to Rudolph, his mouth remains closed.
Visible crew/equipment: Sometimes, especially at night, you can see the lights of the equipment reflect off of Tony's glasses. We know this isn't the moon or a car light because for one thing it's the wrong shape and when Rudolf is sucking blood out of the cow there is no moon or car nearby. So there is only one place the light could have come from, and that would be the crew equipment.
Continuity mistake: When Tony puts Rudolph into the chest at the end of his bed, he climbs into bed with his red tee-shirt on. In the next shot, his red tee-shirt is neatly folded up, and is sitting on the chest, and Tony has now got a pajama top on.
Audio problem: When Tony throws a stone at Rookery's light to save the Sackville-Baggs, he pumps his arm and says "Goal!", though his mouth says "Yes!" Also, Rudolph, in response to this, says "Wow!", although his mouth forms the words "Oh, man!"
Continuity mistake: Right before Anna comes into Tony's bedroom (when she teaches him to whistle), Tony is sitting on his bed wearing a sweatshirt and jeans. When Tony hears the approaching footsteps he dives under the covers, and he is wearing his nightshirt.
Continuity mistake: In the scene where Tony first meets Rudolph. Tony has his fake vampire teeth in and is pretending to bite his teddy-bear. He uses tomato sauce to simulate blood and has it all over his face. He uses his left sleeve to wipe his face completely clean, yet for the rest of the scene the tomato sauce keeps appearing and disappearing and changing shape.