This one's a bit more of a deep cut, but I think it's relevant. It's certainly very interesting.
I don't know how popular or well known the Marx Brothers as a whole are with most Americans these days, but from my experience Groucho Marx is a very familiar name and certainly a familiar face. At the very least, everyone knows what Groucho glasses are. They're those glasses with the big eyebrows and giant nose that you put on to look like Groucho, although the cigar is normally not included.
Now, Groucho, along with Chico, Harpo, Gummo, and Zeppo, were of course not the real names of the Marx brothers. Would you believe that the idea for their stage names came from a comic strip? Would you also believe that one of them in particular was lifted wholesale from said comic strip? It's true.
Gus Mager is best known among comic strip enthusiasts as the creator of the great strip Sherlocko The Monk. Sherlocko was, as you can guess from his name, a great detective, and he also had an assistant named Watso. Neither of them were monks in the Benedictine or Buddhist sense. "Monk" in this case is short for monkey, and Sherlocko and Watso were not the only Monks that Gus Mager drew. The very first was Knocko the Monk, who had his own strip. Others such as Rhymo, Henpecko, Braggo, Coldfeeto, Tightwaddo, Masherino, Grafto, and, yes, even Groucho joined later on and were eventually given a new strip called "The Monk Family." There were also a couple who didn't fit in with the obvious naming convention of the rest, such as Mufti and Freshy. Still, most of them began with some type of description of their character and ended in "o."
Now, the Marx Brothers themselves didn't decide to give themselves these names from the comic strip. That was done by one Art Fisher, a comedian who knew the Marx Brothers and decided to give them all nicknames based on the Monk Family naming convention. They obviously stuck, and went on to be much more famous than the comic strip they were named after.
As for Sherlocko, Arthur Conan Doyle was none too pleased with the similarity of Sherlocko's name to the name of his creation, Sherlock Holmes. Mager decided to have him renamed Hawkshaw the Detective and to have Watso renamed The Colonel. Over time, they were also both de-monkeyfied, so eventually they looked basically human.
For more info, see the articles at Don Markstein's Toonopedia, the Lambiek Comiclopedia, and at Marxology.