Lothar the Grouch is an alien Grouch from the seventh moon of the planet Zurkon. He sends a hologram message billions of miles to Oscar the Grouch on Earth via R2-D2 in a 1980 episode of Sesame Street.
The message is "Oscar the Grouch, get lost!", to which Oscar replies "What do you know? There is intelligent life in outer space." At the end of the episode, Oscar gives a gift to R2 to deliver to Lothar (a jar of candy with a spring-loaded snake inside).
Oscar later meets Othmar, another Grouch from the seventh moon of Zurkon.