There's a ton of these on the NicoNico Douga site (in fact, the original post has the automatic mario version of the NicoNico Douga theme song). I'll see if I can post them to my Japanese blog (it allows me to embed those videos in it). One version did it for a 15 MINUTE SONG. Completely nuts :X
Edit Okay here it is:
http://ameblo.jp/shiroryuu/entry-10095412390.html
For each video, click on the:
"再生"
button, otherwise it will take you to the site instead. One of the features of NicoNico Douga is the ability to overly user comments on the video. For those of you used to youtube, this might seem a bit weird. You can turn off comments by pressing the bird button on the lower right hand side of the player once.
The videos are:
1) The NicoNico Douga song with auto mario posted by the op. I put it there because it's a personal favorites list
2) GONG by JAM Project
3) A Touhou Project song, I'm too lazy to translate the name
4) A Hatsune Miku song because, well look at my sig
5) Wind Climing, the op song of a very very old school anime about magic girls 'n stuff