From Muppet Wiki

Characters and alter-egos assumed by Rowlf the Dog in Muppet productions.

Picture	Name	Production	Notes
	Dizzy Salami	Commercial for Esskay Meats	Rowlf plays scatting hipster Dizzy Salami of the Luncheon Meat Five.
	Sherlock Holmes	The Muppet Show, episode 103	Sherlock Holmes and the Case of the Disappearing Clues: Rowlf plays Holmes to Baskerville's Watson.
	Dr. Bob	The Muppet Show	From the Veterinarian's Hospital sketches, a punning surgeon who's gone to the dogs.
	King Arthur	The Muppet Show, episode 305	In the Muppet production of "Camelot", Rowlf plays King Arthur.
	Father in "Jabberwocky"	The Muppet Show, episode 506	The Muppet production of the poem "Jabberwocky" features Scooter as the young man and Rowlf as his father.
	a gobagoo	Sing-Along, Dance-Along, Do-Along video	Rowlf fails to do what he has to do, and thus turns into a gobagoo.
	Merlin	The Jim Henson Hour episode 102	In a variation on his Dr. Bob role, Rowlf plays a punning wizard.
	Elvis Presley	The Jim Henson Hour episode 107	Merlin pulls a sword out of a knight patient's head with the understanding that he will become "the King." He promptly turns into a Muppet caricature of Elvis (still sporting Rowlf's ears and voice) and sings "Hound Dog."
	Dickensian Rowlf	The Muppet Christmas Carol	Rowlf had a brief and silent role as the piano player at Fozziwig's Christmas party along with The Electric Mayhem.