Puppeteer Caroll Spinney, the voice of Big Bird and Oscar the Grouch, is leaving Sesame Street after 50 years, CBR reports.

Spinney, who has been with the show since its debut in 1969, will have his last recording session this week. The 84-year-old actor has appeared in thousands of episodes of the beloved children’s series, according to Sesame Workshop.

Spinney explained during to The New York Times that his fading health was the impetus for leaving the show. He was forced to stop serving as the actual puppeteer for Big Bird and Oscar in 2015. Big Bird and Oscar will be recast following Spinney’s departure form the series. Some of his final recording session will be included in the Sesame Street 50th anniversary special set to air in 2019 on HBO.

Big Bird and Oscar are among the most popular characters on Sesame Street. Jeffrey Dunn, the president and chief executive for the Sesame Workshop, told The Times that, “Big Bird has always had the biggest heart on Sesame Street, and that’s Caroll’s gift to us… I think it’s fair to say Caroll’s view of the world and how we should treat each other has shaped and defined our organization.”