And pretty well, mind you. But he does play Super Mario World by using his nose to blow into a musical instrument.
NicoNico user Wakou does this by using a program called Audio Pad, which allows him to control Mario with sound (which is why he doesn't talk during the video, because any noise impacts the character's movements).
For example, if Wakou plays "do" on the recorder, Mario moves up. With "mi", Mario moves down. "Re" causes Mario to move left, while "fa" makes Mario move right. The sound "sol" is mapped to the B button, and "ti" is the "Y" Button, etc. Complex, maybe, but you gotta love how excited he gets at the end.