From Mark Evanier's very fine blog News from ME: In 1962, Screen Gems, the television division of Columbia Pictures, tried to produce a Marx Brothers television show. The fact that Chico had passed away in 1961 did not deter the project, as it was intended to be done in Claymation animation (called Tri-Cinemation by the production).
Evanier says little is known about the project's backstory, but there are rumors.
Some folks have said that the animation was the work of Louis Bunin, an artist and puppeteer who made a number of films not unlike this one. I have no idea how true that may be.
Some folks have also theorized that Groucho's voice was done by Groucho himself or Dayton Allen or Pat Harrington, Jr., the latter two being comedians who occasionally replicated Groucho's voice for commercials or cartoons. I don't think it sounds like any of the three and Chico's doesn't even sound to me like a professional actor.
And Evanier would know; he's an animation expert and animation voice director.
The test film they made clearly shows why the project didn't go anywhere. The comedy falls totally flat.
