Marder has a missive in the fifth issue of Arn Saba’s NEIL THE HORSE comic, with one illustration of a very excited Bean printed, though the reply (in character from Neil the Horse) mentions that the whole letter was illustrated in that style. In the letter he compares the comic to both Oz books and some magazines he vaguely remembers that I don’t know at all, but a websearch for Timbertoes does reveal this site which seems to fit what he’s talking about, so the magazine might be Highlights For Kids or whatever the equivalent back then was. He also credits something like NEIL THE HORSE being there as being an inspiration for his own work.
Arn Saba’s NEIL THE HORSE was one of the strangest books of the 1980s, mixing a nostalgia for old animation, comic strips, children’s activity books and musical comedy in various experimental combinations. It had 15 issues published by Aardvark-Vanaheim and Renegade from 1983 to 1988. Saba seems to be out of comics entirely now. You can read a detailed overview of the series at Indy Magazine.