Mighty Man & Yukk was one of the components of the Plastic Man Super Comedy Adventure Show in 1979. Mighty Man was an amalgam of a number of different heroes, including Batman (Mighty's alter ego was wealthy playboy Brandon Brewster), the Atom (Mighty shrank down in size to fight crime), and Blue Falcon (Yukk is Mighty's canine sidekick, but far uglier than Dynomutt---in fact, the two dogs share the same voice actor, Frank Welker). Yukk's gimmick was that his face was so gruesome, he could literally stop a clock, hence the toy doghouse-mask he had to wear 24/7.
Here's a typical Mighty Man adventure, as our intrepid heroes battle Big Mouse and Magnetman.
Edit, 10/17/17: Had to change the video again, this time using Dailymotion.