The iconic fast-food mascot could sometimes be found greeting customers near the entrance to a McDonald's store. If you were lucky enough, a real-life version would make a muck at your birthday party.

It’s not often that a mascot for a fast-food franchise will detail the discomfort prompted by hemorrhoid surgery in a national television advertisement. But Mr. Delicious rarely played by the rules.

Because of the social media trend, clowns went from a childhood entertainment to the stuff of nightmares. McDonald's ...