Nien Nunb is a small, jowled, mouse-eyed native of Sullust, the world that served as the staging area for the Alliance Fleet prior to the Battle of Endor. Nunb was co-pilot to Lando Calrissian aboard the Millennium Falcon during that historic event. Many of his fellow Sullustans also served as Alliance starfighter pilots in the battle. Nunb spoke the liquid, chattering tongue of the Sullustans, a language Lando understood.
As a member of the Rebel Alliance, Nien Nunb was chosen by Lando Calrissian to co-pilot the Millennium Falcon during the Battle of Endor. Together they flew the Falcon into the superstructure of the Death Star, knocking out the reactor core which brought the Empire to a fiery end.
Lando Calrissian volunteered to lead the starfighter assault on the Death Star during the Battle of Yavin. At the urging of Han Solo, Calrissian once again piloted his old ship, the Millennium Falcon, and chose Nien Nunb as his co-pilot.
During the Battle of Yavin, Nien Nunb acted as Lando Calrissian's co-pilot aboard the Millennium Falcon. Together they lead the starfighter assault on the Death Star, attacking its reactor core and causing its destruction.
While evading TIE Fighters and narrow corridors, Nien Nunb co-piloted the Millennium Falcon, alongside Lando Calrissian, into the Death Star's superstructure. There they fired two concussion missiles into the space station's massive reactor core causing its destruction and sealing the Empire's fate.