Caroll Spinney, the veteran actor and puppeteer who provided the voices for Sesame Street’s Big Bird and Oscar the Grouch, is retiring after almost 50 years as a key part of America’s most well-known children’s television show.

Spinney will work on a final show this week, which will be used for Sesame Street’s 50th-anniversary celebrations in 2019. He is retiring having worked on thousands of episodes of the programme, which debuted in 1969.

“I always thought: ‘How fortunate for me that I got to play the two best muppets?’” he told the New York Times. “Playing Big Bird is one of the most joyous things of my life.”

Under his wing … Caroll Spinney as Big Bird.

Photograph: Mark Lennihan/AP

In 2015, Spinney told the Guardian that Big Bird was initially a bit part before he developed it into one of the most recognisable figures in children’s TV. “At first, Big Bird wasn’t a major character, and Jim Henson, who developed the characters, said to play him like a goofy yokel from the country,” said Spinney.

“But it felt more natural to me to play him as a child, like a big kid. When I tried it out, Jim and the writers agreed, and soon Big Bird grew into a worldwide superstar.

“I’d worked on a few different shows before I got the job playing Big Bird and Oscar the Grouch in the first season of Sesame Street,” he added. “I had no idea I’d still be doing it more than 45 years later.”

In 2015, an autobiographical documentary, I Am Big Bird, was released in cinemas, described in the Guardian as “a massive nostalgic sugar rush” to anyone who grew up in the 70s or 80s.

“Big Bird has always had the biggest heart on Sesame Street, and that’s Caroll’s gift to us,” Jeffrey Dunn, the president and chief executive of Sesame Workshop, told the New York Times. “I think it’s fair to say that Caroll’s view of the world and how we should treat each other has shaped and defined our organisation.”