I never quite understood the difference between a YTPMV and a MAD. Is it simply that MADs are made by Japanese people and uploaded to niconico, and YTPMVs are uploaded to YouTube?
Anyway, webm related is my favourite by far: https://youtube.com/watch?v=qKGkA5mn-jY
They mean the same thing. Youtube Poop Music Videos and Tapes of Madness both utilize samples from popular tv, memes, etc., and replicate popular music.