The "Curse Word" episode was, IMHO, the funniest episode of South Park I've ever seen, with honorable mention going to "Sexual Harassment Panda" and "Ike's Weewee."
All these years we thought the Black Plague was caused by rats; now we know it was caused by a "curse" word.
I laughed hysterically throughout the episode. I laughed so hard I almost Sh**.
BTW, "Dinosaurs" did a vaguely similar plot. Only the taboo word used on TV was "smoo" (a fictional prehistoric curse word).