Underdog has been a surprisingly durable cartoon character and series. Produced during the 60s and 70s it has lasted all the way to 2005's live action movie. That movie had almost nothing in common with the old cartoon, unfortunately. Still, it says something about the staying power of the franchise.
Underdog was a blatant parody of Superman. Underdog's secret identity was Shoeshine Boy, who would take a special energy pill and transform in Underdog. Underdog would usually have to save Sweet Polly Purebred, the Lois Lane stand-in.
Like most long-lasting cartoon series, Underdog had a great theme song. "Here I come to save the day!"
Interestingly, Underdog has stayed in the public consciousness for so many decades partly as one of the more famous floats in Thanksgiving Day parades.
Underdog's animation was often a bit crude, and the storylines were simplistic, but the show had a certain sweetness about it that endeared it and the character to its many fans.