Prunella

From Muppet Wiki

Prunella guest starred in Episode 3119 of Sesame Street. A gray grouch of British extraction, Prunella drives through Sesame Street while touring the United States, and Oscar the Grouch briefly develops an attachment to her.

The pair sing an ode to all things grouchy, "Wouldn't It Be Yucky," a parody of "Wouldn't It Be Loverly?" from My Fair Lady.