Dr. Kvetch is a Grouch doctor who made recurring appearances on Sesame Street in the 1980s and 1990s.
He appeared as early as Episode 1599, making a house call to Oscar's, discovering he's come down with the "Grouch Flu," an ailment that makes Grouches act nice.
He appeared later in Episode 2630, now diagnosing Oscar's niece Irvine with the same infliction. Dr. Kvetch prescribes rest, fluids, and staying away from nice people. He re-appears at the episode's end, when Oscar is now infected with the Grouch Flu. However, the doctor flees the scene, fearing for his own safety.