Yabba Dabba Doo! The Happy World of Hanna-Barbera is a 1977 American live-action/animated television special produced by Hanna-Barbera Productions which premiered on CBS on Thanksgiving Day, November 24, 1977. The special is hosted by Gene Kelly with special guests Jonathan Winters, Cloris Leachman and Lorne Greene celebrating the 20th anniversary of the award-winning partnership of animators William Hanna and Joseph Barbera. It covers Hanna-Barbera creations from their first collaboration effort in 1938 working at Metro-Goldwyn-Mayer cartoon studio, to their formed partnership of Hanna-Barbera Productions in 1957, and all the way through to Heidi's Song, an animated theatrical feature that was currently in production at the time, which would see release five years later in 1982.