Groucho Marx? ZZZZT, wrong answer.
Actually I am old enough. I got my shows mixed up. Pluck your magic twanger froggie was from the Buster Brown show, which I used to watch all the time as a kid. Groucho had the duck that dropped down with the magic word. Got my ducks and frogs mixed up. Thanks for catching that for me. Hope Vicomte 13 reads this to know it was from Buster Brown and not Groucho Marx, although I could hear Groucho saying the froggie phrase w/emphasis on sexual innuendo, as he was a bit of a dirty old man.
Right you are. Some folks are saying we are remembering the wrong show, but I think Andy Devine and the others were copying Froggies's original schtick later in the '50s TV era.
My 69 year old memory card may not be what it once was, but I distinctly remember many Saturday mornings spent lying on the floor of my pal Eddie's front porch in Newark NY eating purple Concord grapes from his dad's backyard arbor and listening to Froggie the Gremlin on the Buster Brown Kids radio program. Also Grand Central Station, Jack Armstrong the All American Boy, Plastic Man, and a few others whose names have slipped my mind.
That was simple, classic Americana of that day and time, and life was good for this 4th grader and his pals on Saturday mornings.