Sweet Polly Purebred

Underdog is an anthropomorphic dog, who is a superhero 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 threatened, Shoeshine Boy ducked into a telephone booth where he transformed into the caped and costumed hero, destroying the booth in the process when his superpowers were activated. In the live action film, he appeared as a beagle who became Jack Unger's pet. In 2008, he appeared in a Super Bowl advertisement for Coca-Cola.

Underdog is voiced by Wally Cox in the television cartoon. In the film adaptation, he is voiced by Jason Lee and portrayed onscreen by a lemon beagle named Leo sporting a red sweater and a blue cape.

Sweet Polly Purebred is a female anthropomorphic dog TV news reporter and Underdog's love interest; she serves as the damsel in distress of most episodes. When being pursued by an antagonist, Polly is apt to start singing, "Oh where, oh where has my Underdog gone? Oh where, oh where can he be?", in a whiny voice, hoping for the object of her affections to come and rescue her. Polly's face is slightly similar to that of Underdog's, with a large muzzle and nose, she wears her platinum blonde hair styled in a pageboy, and her wardrobe consists of a black skirt, white shirt, red sweater, and black high-heels. In a few episodes it is hinted that Polly shows her love for Underdog. For example, in the episode "March of the Monsters", she is caught by a robot and calls for Underdog. He then saves Polly, but after Underdog uses his supersonic hi-fi voice and breaks all the glass, the townspeople complain about his voice. However, Polly defends the hero and tells the people that they should thank him for saving everyone from the robots. She then goes to reward Underdog with a big kiss, but the hero backs away and flies off. Also, in the episode "The Vacuum Gun", when Polly is caught by Simon Bar Sinister's vacuum gun, she calls for Underdog and her song annoys Simon. Later in the episode, she retrieves Underdog's ring.

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Wikipedia