(Orson Welles, Oscar Levant and Fred Allen were among those who would go on to become, if not regulars, at least part of the show's extended \"family\")
Realizing this might be one of my few chances to talk about radio game shows on here...
You're more right than you may even realize about Levant. He was a full-fledged regular on \"Information, Please\" for much of the run, but unlike the show's other two regular panelists, he was on every other week. Best I can tell, Orson Welles only made a single appearance on the show, though Fred Allen did visit half a dozen times or so.
One of the more disappointing things today (speaking as someone who has all the 200+ episodes that survive) is that the guest list really rarely included show-biz types. Sure, it's a joy to listen to Groucho or Welles or Allen or Alfred Hitchcock play along, and truly amazing to hear historical figures like Alben Barkley, Wendell Wilkie or Henry Cabot Lodge subject themselves to potential humiliation on a quiz show, but in general, the majority of their \"famous\" guest panelists have pretty much been lost to history.
FYI, I play a modified version of \"Information, Please\" on my cable channel called \"Stumpers\" in which we use teachers and principals as contestants. It's crudely produced (hey, the crew is high school students!) but it's one of the more popular things we do.