Bud Luckey, the Oscar-nominated animator who designed Toy Story's Woody, has died, his son has announced.
Luckey, who was born in 1934, also worked on films like A Bug's Life, Monsters, Inc and Cars.
He also voiced characters including Chuckles the Clown in Toy Story 3, Rick Dicker in The Incredibles and Eeyore in the 2011 Winnie the Pooh film.
He made his name working for Sesame Street, where he was responsible for the popular animated counting songs.
Luckey died after a long illness at a hospice in Connecticut on Saturday. He was 83.
"He loved his work but got even greater satisfaction from seeing others enjoy it," Andy Luckey wrote on Facebook.
Bud Luckey joined Pixar in 1992 - he was the fifth animator hired by the company.
Pixar and Disney animation chief John Lasseter has previously called Luckey "one of the true unsung heroes of animation".
Before the first Toy Story film came out in 1995, he suggested making Woody - voiced by Tom Hanks - a cowboy instead of a ventriloquist's dummy, which was the original idea.
"People had kind of a spooky feeling about ventriloquists after The Twilight Zone," Luckey said.
He was nominated for an Oscar in 2004 for his short film Boundin'.
Toy Story 3 and Coco director Lee Unkrich was among those paying tribute.
So sad to hear that Bud Luckey passed away today. He voiced Chuckles in Toy Story 3, but that was the least of his many amazing accomplishments. A tweet is not sufficient to sing his praises. pic.twitter.com/VR2ORNzwiP— Lee Unkrich (@leeunkrich) February 25, 2018
Prior to Pixar, Luckey created and animated educational number cartoons for Sesame Street including The Ladybugs' Picnic, featuring the number 12.
In a 2004 interview Luckey said: "I like to think 30 years ago, I used animation to teach kids their numbers and now these kids are teaching me how to animate with numbers. So it was a good deal."