"Rooby-Rooby-Roo". Scooby was voiced by Don Messick until the voice actor's death in 1997. Messick is also known for providing the voice of the dogs Astro on The Jetsons and Muttley (who snickered). The characteristic voices of Scooby and Astro are so similar that Astro's signature phrase, "Ruh-roh!" ("Uh-oh!") is popularly