The puppeteer behind Sesame Street characters Big Bird and Oscar the Grouch has been described as an "artistic genius" with a "kind and loving view of the world" after his death at 85.
Caroll Spinney died at his home in Connecticut after being diagnosed with movement disorder Dystonia, Sesame Workshop, the educational organisation behind the show, said.
Caroll was mentored by Sesame Street creator Jim Henson, who died in 1990, and the pair were friends for decades.
His career saw Big Bird visit China with Bob Hope, dance with the Rockettes, and be celebrated with a star on the Hollywood Walk of Fame.
The famous bird also appeared on a US postage stamp, and was named a Living Legend by the Library of Congress.
A statement from the Henson family said: "It was a moment of creative destiny when Caroll Spinney met Jim Henson.
"The gentle performer, who would bring to life two of the most beloved residents of Sesame Street, could perfectly convey the humour and heart in our father's creations.
"Big Bird was childlike, without being childish. And Oscar the Grouch reflected universal feelings we all share, no matter our age.
"Those of us privileged to work alongside him and call him friend saw first-hand that he cared so deeply about what these characters represented and how they could truly create change.
"Caroll's decades-long commitment to bettering the lives of children all around the world is his true legacy. That he could do this work so brilliantly, responsibly, and with such infectious love and joy, is his gift to us all."
The not-for-profit Sesame Workshop said: "Caroll was an artistic genius whose kind and loving view of the world helped shape and define Sesame Street from its earliest days in 1969 through five decades, and his legacy here at Sesame Workshop and in the cultural firmament will be unending.
"His enormous talent and outsized heart were perfectly suited to playing the larger-than-life yellow bird who brought joy to generations of children and countless fans of all ages around the world, and his lovably cantankerous grouch gave us all permission to be cranky once in a while."
Sesame Street co-founder Joan Ganz Cooney said Spinney's contributions to Sesame Street were "countless", adding: "He not only gave us Big Bird and Oscar the Grouch, he gave so much of himself as well.
"We at Sesame Workshop mourn his passing and feel an immense gratitude for all he has given to Sesame Street and to children around the world." Spinney is survived by wife Debra and his children and grandchildren.