Original Appearances: Mumbly segments of The Tom & Jerry/Grape Ape/Mumbly Show (1976)
Other Appearances: The Tom & Jerry/Mumbly Show (1976/1977), Laff-A-Lympics (1977-79), Yogi Bear and the Magical Flight of the Spruce Goose
Biography: Mumbly seems to have switched sides during his cartoon career. Originally, he was a police detective dog, working for police chief Schnooker, possibly inspired by Columbo. However, in Laff-A-Lympics, he suddenly appeared as the captain of the villainous Really Rottens team, with the Dread Baron as his right-hand man. Mumbly and the Dread Baron also were the villains in Yogi Bear and the Magical Flight of the Spruce Goose.
Group Affiliation: Really Rottens
Miscellaneous: No explanation was given for why Mumbly switched sides in the cartoons themselves. It is possible that the reason Mumbly and the Dread Baron were used in Laff-A-Lympics instead of Muttley and Dick Dastardly is because the latter duo were created as a co-production with Merrill Heatler and Bob Quigly Productions, so Hanna-Barbera did not fully own the characters. Along with the strong resemblance to Muttley visually and vocally, this is probably why there's most of the confusion between the two characters.