South Park's cigar-smoking, cussing, violent, totally corrupt Hollywood magnate Mickey Mouse is epic and 100% accurate. It's probably why Disney didn't sue them.
Well, Disney didn’t sue them because they would have lost. Satire is a protected use.
Disney suing them would have just been lawfare, but the South Park guys and Comedy Central (and whichever conglomerate owns them) are big enough that Disney can’t intimidate them just by threatening a lawsuit.
Hilarious episode!