From Muppet Wiki

The Willy Muppet is a caricature of Muppet designer Kermit Love. He more closely resembles Love's Sesame Street character Willy, particularly as seen in a sketch with Grover as he passes a ONE WAY sign with a food cart; an image indicative to the Willy character. He also appeared in "Bus Stop," waiting for the bus, and during the song I Love a March.