John Dunning's great On the Air, The Encyclopedia of Old-Time Radio details it in depth, but suffice it to say that Groucho Marx didn't want to do it, the radio brass didn't think it would work, and the only reason it got on the air was a man named John Guedel.

"I figured he'd be great working with people out of an audience," Guedel recounted. "When people were being funny, Groucho could be the perfect straight man, when the people played it straight, Groucho couldn't miss with his own comedy." Sometimes, even the obvious has to be proved. The studio brass were unsure. Groucho himself had to be convinced it would work, and he had tried much more hair-brained schemes to make a buck in his films. Just ask Rufus T. Firefly. And everybody knew the man could deliver a line when it was written, and he had a lightning wit. Could it work live on radio with an audience hanging on every word, with rank amateurs.

George Fenneman was Groucho Marx Master of Ceremonies, with Mike Wallace doing the commercials for Elgin-American. The contestants were absolutely real audience members, but the show's staff would pair r them in a novel or interesting way, such as by occupation, opposites in age, etc. And the talk was absolutely spontaneous, although the show was edited to keep the best lines. Was Groucho's great career in showbiz dedicated to being brash and getting off great lines? You Bet Your Life!