The Smurfs
From Muppet Wiki
Brainy Smurf and Kermit Clock in Cartoon All-Stars to the Rescue
The Smurfs were created by the Belgian artist Peyo in 1958 and later starred in a successful Hanna-Barbera animated series.
Some of the Smurfs, including Papa Smurf and Brainy, appeared with the Muppet Babies in the 1990 animated television special Cartoon All-Stars to the Rescue.
References
In episode 205 of Muppets Tonight, Don Rickles is hired by Ernst Stavros Grouper to act as therapist and boost company morale. Rickles reports after having met with the Muppets: "I talked to your happy little Smurf friends."
