This was an anthropomorphic parody of Superman and similar heroes with secret identities. The premise was that humble and lovable Shoeshine Boy, a cartoon dog, was in truth the superhero Underdog. When villains theatened, Shoeshine Boy ducked into a telephone booth in which he transformed into the caped and costumed hero, destroying the booth in the process. Underdog, unlike Shoeshine Boy, almost always spoke in rhyme.
Unlike Superman, Underdog's super powers are apparently not a natural part of his physical makeup. When he is not Underdog, he is incognito as a shoeshine boy. He dresses in a phonebooth much like Superman when trouble calls, and that is when he gets his Super Powers. When Underdog's superpowers begin to fail, he must take an "Underdog super energy pill" to replenish them. He keeps one of these pills inside a special ring he wears at all times. (Several episodes of the cartoon show him losing the ring and being powerless until he gets it back.) When the Underdog series was syndicated in the 1980s and 1990s, the scenes of him actually taking his energy pill were edited out. Animation fans lambast this as a form of political correctness, as they believe the scenes were removed in order to prevent any glorification of "drug use."
Wally Cox was Underdog/Shoeshine Boy's voice actor. Norma McMillan played Polly Purebred.
The show ran in two or four part serial episodes. Usually two brief episodes were shown in a single show, along with cartoons like Go Go Gophers, King Leonardo, Klondike Kat, Tennessee Tuxedo, or The World of Commander McBragg. None of these cartoons ever reached Underdog's popularity. Underdog's balloon is a recurring feature of the Macy's Thanksgiving parade. The show is also remembered for its clever theme song, whose lyrics went: