Revealing mistake: Near the end of the film, when the people are in the house fighting the Leprechaun, one of the characters is using a shotgun. The Leprechaun rides up and down a hallway on a skateboard and the character with the shotgun shoots at him, missing not only the Leprechaun, but everything else as well. Unless he was using a round full of confetti that I've never heard of, he should be shooting the wall and everything else in sight, yet nothing at all is hit.
Revealing mistake: When Tori and others are fighting the leprechaun in the kitchen the wall phone rings and she picks up the hand set. It's the leprechaun on the line and in fear and anger, she slams the hand set back in place and tears the entire phone off the wall. As the phone rips away, it's obvious there is no phone line connector on the wall, only a nail the phone was hanging on.