That's exactly what I thought, too...that episode of South Park was around 2007 IIRC. Which actually made me suspicious - it's almost too similar. Here's the isolated clip, with some YouTube comments:
Now, I know to take YouTube comments with a grain of salt, and I'm generally not one to shout fake, but....
Fake?
I'd put my money on fake over real. In a world where Jordan Peele and some tech folks can combine to make a fake Obama video that actually warns people about fake videos...I'm not sure that clip is real, for several reasons:
1) The silence is deafening. It's like they're giving time to let the shock come in.
2) The "N" guy just seems....like it's separate in terms of video.
3) Let's play logic. First letters to be picked? TRNSLE. Say they skip the "N". You get _L__ ____ER. The N is just begging to be picked, even if you buy an A making an N seem unlikely in the first word.
4) If this were ever actually ON Wheel of Fortune, the whole episode would probably wind up on the cutting room floor. Recreate it, and run the "portions of this episode may have been recreated" disclaimer that's necessary thanks to Standards and Practices and the Twenty-One/Quiz Show scandal. When the guy guesses "N", have him guess "B", or even "P".
