Nadir first appeared on The Muppet Show in episode 402, where he invaded the Swinetrek and ordered his chicken stormtroopers to peck the crew to death. He appeared again later in the season, in episode 417, as part of a full-blown Star Wars parody.
His name has often been incorrectly spelled Dirth Nader. In the late 90's, Jerry Juhl wrote to Danny Horn of MuppetZine, correcting him on the spelling. The name is a play on words -- "Dearth" means "lack of," and "Nadir" means "the lowest point."
A grown-up Gonzo appears in the 1985 Muppet Babies comic book The Big Space Adventure in a similar outfit, playing King Nonzo of Onzo, in pursuit of Baby Piggy in her Princess Leia costume. As he takes his helmet off, he realizes in shock that he resembles "ugly," little Baby Gonzo. In Tales of a Sixth-Grade Muppet, the protagonist imagines several scenarios for what it will be like to meet Gonzo, one of which features Gonzo as Darth Vader in his meditation chamber.
In 2008, Gonzo's Star Wars likeness was produced as a PVC figure. Other merchandise has followed including pins, t-shirts and posters.