Mojo, the best music magazine in the world, introduced me to this. So blame them, not me.
There's a group called the Legion of Rock Stars, and their MO is really quite simple. They put on headphones that cancel out all noise, listen to and play along with the same song, and dub the results over video of the original hits by the original artists. The results are... really quite painful.
There are a lot of these to choose from; if you're a fan of the Shaggs and/or you like what you see here, go here for more.