The collection of illustrations, which includes an original Polaroid of Miss Piggy and Henson's handwritten pitch of story ideas, marks the early stages of development for the lovable characters including Kermit the Frog that have become an American pop culture staple.

"The photos and sketches showed Henson's vision as he created one of the most popular shows of all-time," auctioneer Nate Sanders said in a statement.

The complete Muppets lot is expected to fetch between $35,000 and $40,000 at the July 31 auction.

Henson's characters, which include Kermit, Miss Piggy and Fozzie Bear, helmed "The Muppet Show" on TV between 1976 and 1981, before appearing in numerous films including 1992's "The Muppet Christmas Carol," and most recently, 2011's "The Muppets" movie.

(Reporting By Piya Sinha-Roy; Editing by Bob Tourtellotte and Marguerita Choy)

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