(Got this from a thread on Destructoid.)

This Hands-Free Super Mario World Level Plays Sweet, Sweet Music

(You have to click on the link until I figure out how to embed this.) 

By now, you must have seen the custom made Super Mario World levels that require no player, no controller to pass. They simply let Mario and Yoshi do their thing, as buttons, switches and blocks boost them through each level. None of those user created levels are as impressive as this 11-minute monster, which uses the sound effects from those switch-hits and Koopa Troopa stomps to make beautiful music. My untrained ears can pick out but a few recognizable tunes—Mega Man 2 and Super Mario World, I don't know from Haruhi and Lucky Star—but song list help in the comments is more than welcome. Thanks to Spann for pointing us in its direction.

It was on GT this week, and yups it is impressive :).

Hasn't this been around for a while? My friend showed me this at work two days ago, and I could've sworn I had seen it months ago.

Or am I just going crazy??

I can't believe Kotaku's power level is so low they don't recognise the Nico Nico medley. It's a collection of popular meme videos from Nico Nico Douga, a hugely popular Japanese YouTube-like site.

There's literally dozens and dozens of different versions of it, all of them awesome. Try searching with "nico nico kumikyoku" or 組曲『ニコニコ動画』 to find more of them.

I could type a huge post explaining every song in it and why they're so cool, but you'd probably be better off just googling.

The link just takes us to a login screen. 

Good video

Yeah, you need to register in order to access Nico Nico. Keeps those silly gaijin out. =P

I meant you can search for that stuff on YouTube, and find plenty of stuff. There's also a decent set of instructions on how to register on GAF.

That was epic, Love it how the music and the sound effects matches and goes along with it

wow that was so amazing

That was unbelievable. The effort it must've taken to pull that off, I can't imagine. Just Woah......