Nightwing
Although Nightwing is commonly associated with Batman, the title and concept have origins in classic Superman stories. The original Nightwing in DC Comics was an identity assumed by alien superhero Superman when stranded on the Kryptonian city of Kandor with his pal Jimmy Olsen. Drawing inspiration from Batman and Robin, the two protect Kandor as the superheroes Nightwing and Flamebird. Following the Crisis on Infinite Earths continuity reboot in 1985, Nightwing was re-imagined as a legendary vigilante from Krypton whose story inspires Dick Grayson's choice of name when he leaves behind his Robin identity.
Alternative versions of Robin
It wasn't revealed until one of the later runs of the Teen Titans that this was not Dick Grayson, in fact his true identity was never uncovered. After this storyline, this version of Nightwing has not been seen since. Whether this version existed at all, after the events of Infinite Crisis or would later to be revealed to be an alternative Dick, Jason, or Tim, is unknown.