Unbeknownst to me, "some guy" isn't actually some guy. He's Keenan Cahill, celebrated bedroom singer and aspiring hip-hop artist. Take a look at the video and wait for the sweet spot at 1:20:
50 Cent! What are you doing here? Perhaps some viral marketing for your new single "Down on Me"? What a world we live in: actual celebrities using YouTube celebrities as sales props. Granted, Cahill was on Chelsea Lately so he's not totally green, which is the way we talk about YouTube celebrities now, but still. Cahill: you are on your way.