Mister Blaize links me to the best stuff.
Reggie Watts - F*ck Sh*t Stack (It's basically every hiphop joke Flight of the Conchords ever made and then some, all in one pretty catchy song)
Click to view
And then this piece of joy - Lady Gaga's Bad Romance on a Korg Monotron and Kaossilator.
Click to view
If it weren't for the exsistence of Elbow's version of
Independent Woman (now with bonus kittens) that would be the best cover version ever. By the time they got to the "walk, walk, fashion baby" bit I was nearly dying with laughter.
ETA: OH MY GODS. There's also a
Justin Timberlake medley, and it's even better than the Gaga cover. It has a theremin! And a keytar! And a Yorkshireman singing "look at them 'ips"! Actually am dying from the funny now...