Shockwave commissioned Parker and Stone to push the envelope back in '99, toward the end of the dot com bubble. They were apparently paid a lot of money, given free reign, and Shockwave figured they'd get something kind of R rated, like South Park. They wound up with this sort of stuff, which was far more offensive than they anticipated. Parker and Stone basically had fun, fulfilled their contract, made a bunch of loot, and fucked Shockwave in the process. Good times!
"Trey and Matt Shock Shockwave?"
http://www.eonline.com/News/Items/0,1,6210,00.html