How many movies have Robert Guenette and William Hanna collaborated on?

They have worked on 2 movies together! Their first movie together was The Hanna-Barbera Hall of Fame: Yabba Dabba Doo II (1979) while their highest rated movie together was The Flintstones' 25th Anniversary Celebration (1986). They have not worked together since The Flintstones' 25th Anniversary Celebration (1986).