Pavlov the Pug Dog

From Muppet Wiki

Pavlov the Pug Dog was interviewed by Rhonda Rat in the "Siberian Tiger & Reindeer" episode of The Animal Show. He appeared again in "Pelican & Flamingo." The character's name is a reference to the famed animal behaviorist Ivan Pavlov, who was particularly known for his conditioning work with dogs.

Pavlov was recycled from an extra Dog City puppet and was later reworked into Piddles for Puppet Up!.