Start with Danny Elfman's Batman theme + Heavy Metal + 8 bit platformer = Epic Fun!

I have not laughed that hard in a really long time.

Did they stop at Batman? No!  They covered all the classic:

Their cover of the X-men theme is amazing, and the Transformers, wow.  I feel guilty I didn't know about this sooner. 

Thanks to Badass Nerd for sharing the video.  This is in rotation for me now.