Usually, when you watch a movie that sends up the horror genre, the movie sacrifices the scares in favor of the laughs. But, in Idle Hands, the movie makers remembered to keep all the creepy touches and startling frights that make a horror movie when they mixed in all the humor.
Not nearly as heavy handed as, say, the Scary Movie franchise, Idle Hands has all the normal trappings of a good teen horror flick: The unstoppable killing evil that has come back, the buddies of the main character who don't understand the danger until it's too late, the horny girl who main character must protect and a brave hero who is a bastion of all that is good in the world to defend us...
OK, so I was lying about that last one. And that is one of the best twists of the film, the main character is a screw-up and doesn't act very heroically until very, very late in the film. In addition to really revving up the laughs, this feature is also what kind of makes this movie stand out from the usual horror fare.
Now, here's the key: While Anton struggles with the evil in his bumbling way, egged on by the wise-cracks of Mick and Pnub, the film delivers actual horror. We get shocks, we get creeps, we get gore and we don't get the "ha-ha got ya!" joke right afterward that you get in most parodies. The scares are real, the deaths are real, the danger are real. And, surprisingly, so are the laughs.