what it is: reverse lip synching (sort of)
where i found it: at work (mishap)
Not long ago I had a music student who wanted to learn the Sly Stone song Family Affair. I went onto youtube and THIS is what I found.
It had me laughing and laughing and laughing, and I figured it was kind of similar to those shreds videos. Months later, through totally different means, I came to find out that this was created by a "band" who has a whole crazy experiential methodology called "the Pure Pleasure Process" for making these kinds of things. Legion of Rock Stars, they're called. Check out this crazy shit.