When it comes to monster movies John Carpenter's The Thing is one of my all time favorites. I've only seen one other movie that can approach the level of paranoia that this move puts forward and I never find myself getting bored of it. It is a brilliant movie that represents the genre's finest.
That being said, I absolutely love this parody song for it. If you haven't seen the movie already, go watch it immediately. It's like five dollars on Amazon, and if you appreciate good horror it will provide you with countless hours of entertainment and cost you weeks of lost sleep.
But yeah, give this song a listening to. It's brilliant! Behold, The Thing The Musical!