Mr. Horvath continues to design new characters, and Ms. Kim still turns them into dolls before they go into mass production.

WSJ: How Did Those 'Ugly Dolls' Come to Be? Their Creators Explain

Allegri has had to work with a rotating cast of characters not by design, but largely because of injuries and inconsistent performances.

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The inked designs provide a guide for the artisan who cuts the picture or design into the wood, producing raised characters that will eventually apply ink to paper.

UNESCO: Culture

Jane Henson helped design many puppets for the hit TV show, whose characters include Kermit the Frog and Miss Piggy, and also worked as a puppeteer.

BBC: Muppets designer Jane Henson dies