When I got my copy of the book "Jim Henson's Designs and Doodles" back in 2001, I really enjoyed looking at Henson's inspirational sketches. But I thought some of the earlier doodles circa 1960, those on pages 10 and 11, looked familiar. After studying them, I realized why. Checking back in my old copy of Walt Kelly's "The Pogo Stepmother Goose" (1954), I found several illustrations that Henson had clearly copied into his private sketchbook. I ran this discovery by Henson archivist Karen Falk, and she readily agreed.
It's no secret that Kelly and Pogo were an early source of inspiration to Henson, and I think these sketches are concrete proof.
Here are Henson's drawings from "Designs and Doodles":
And here are details from Kelly's "Stepmother Goose" illustrations: