Underdog.

Underdog, also known as The Underdog Show, is an American Saturday morning animated television series that ran from October 3, 1964, to March 4, 1967, starting on the NBC network until 1966, with the rest of the run on CBS, under the primary sponsorship of General Mills, for a run of 62 episodes. It is one of the early Saturday morning cartoons. The show continued in syndication until 1973. Underdog, Shoeshine Boy's heroic alter ego, appears whenever love interest Sweet Polly Purebred is being victimized by such villains as Simon Bar Sinister or Riff Raff. Underdog nearly always speaks in rhyming couplets, as in "There's no need to fear, Underdog is here!"