"In the 14 years we've been doing South Park we have never done a show that we couldn't stand behind. We delivered our version of the show to Comedy Central and they made a determination to alter the episode. It wasn't some meta-joke on our part. Comedy Central added the bleeps. In fact, Kyle's customary final speech was about intimidation and fear. It didn't mention Mohammad at all but it got bleeped too. We'll be back next week with a whole new show about something completely different and we'll see what happens to it."
Matt Stone & Trey Parker
Picture above includes a drawing of Mohammad which ironically has aired in South Park's opening credits...
And from the April 25th Episode of The Simpsons: