heheh, that's the kid who got internationally humiliated isn't it? quality.

although it's probably done the rounds a fair bit by now, this is still pretty funny too.
http://www.atomfilms.com/af/content/gangsta_rap_se

Incidentally, I think Gregoshi's right, Vader was guessing that Luke must have been trained by Obi Wan over a longer period than was actually the case, and didn't know about Yoda at that time.