I always find it fascinating when a fictional character is created for a single purpose, but ends up being so much more than that. Many times they are created as an advertising gimmick used to sell toys, greeting cards, cat food, and just about anything else you can think of. Some of them, Rudolph the Red-Nosed Reindeer as an example, prove to be so popular that most people don't realize they were originally created to by an ad agency. There are some of that never leave the realm of advertising, Tony the Tiger for example, that still somehow manages to become bigger than the product itself. The guy, while not as huge as Rudolph still managed to follow in his footsteps, and become more than the cereal peddler he started off as.
The superhero who always spoke in rhyming couplets, Underdog was the brainchild of General Mills, the company behind many of my favorite cereals from childhood. He, along with Tennessee Tuxedo, proved to be so popular they got their own cartoons, comic books, and merchandise. Much like Superman, Underdog hid his greatness behind a mediocre front, Shoeshine Boy. They shared many of the same superpowers, and even had a familiar catchphrase, but that's were the similarities end.
Where Superman was focused on saving the world from extensional threats, Underdog was more concerned about saving his girl from the nefarious villains who just couldn't leave her alone. And while he did in fact have great superpowers, he could never finish a episode without flying into a building, or causing so much collateral damage that I can't even begin to imagine the cost of his cleanups. I would have suggested Karate Kat, who was a janitor by day, for cleanup duty, but he didn't come around until decades later.