Baskerville the Hound was originally created in 1962 for Purina Dog Chow commercials, as a companion to Rowlf. He is a small brown shaggy dog with glasses and a beak-like snout.
Muppet Show appearances: Baskerville appeared in the UK sketch of Episode 103, as Dr. Watson to Rowlf's Sherlock Holmes. In Episode 208, he auditioned as a comedian. This was the only Muppet Show episode in which his name was mentioned (Scooter was the one who mentioned that name). Episode 308 took place at a train station; Baskerville was a conductor at the station.
Performers
Baskerville has been performed by a number of different people.
Jim Henson performed his voice (Jane Henson most likely did the actual puppetry) in the Purina Dog Chow commercials.
John Lovelady performed him in Episode 103.
Jerry Nelson performed him in Episode 106, Episode 116, Episode 208 and Episode 308.
Frank Oz performed him in Episode 110.
Dave Goelz performed him in Episode 524.
Baskerville's name comes from the Sherlock Holmes book The Hound of the Baskervilles. Baskerville's name and design were both considered for Rowlf.