Ernest the Grouch is Oscar's brother. He looks like Oscar, but with big black eyebrows and a scuzzy green mustache.
Ernest first paid Sesame Street a visit during the show's eighth season in Episode 0954 (1977). Oscar decided to prepare an unpleasant surprise for him by decorating his trash can, dressing neatly, and treating Ernest like a gentleman. Determined not to let him have the last laugh, Ernest returned the favor. Soon the two of them were trying to outdo each other. Their grouchiness was returned when they found themselves fighting over a concoction only Grouches would enjoy.
Ernest payed another visit to Sesame Street in Episode 1688, where it is established that he lives in Chicago and fills a similar role to Oscar as the street grouch; the same street Mr. Hooper's brother Arnold Hooper lives on.
Ernest would visit his brother again years later in Episode 2720 (1990). The episode itself is a remake of the one from season 8, with Gordon and Gina replacing Maria, Luis, and Mr. Hooper.
The first version of Ernest was recycled from an Oscar puppet used during the early to mid-1970s (one that had moving eyes), and wore no clothing. The second version wore a white collar and blue bow tie.