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.
Dick Grayson
Dick Grayson has taken on the identity of Batman on a few occasions. In the aftermath of "", Grayson initially declines taking up the mantle of Batman while the original was recovering from a broken back as he feels Nightwing is a hero in his own right and not Batman's understudy, but after the events of the "Zero Hour" miniseries later that year, he replaces Bruce Wayne as Batman, beginning in "Robin" #0 (1994) and extending throughout the "" storyline in 1995. Dick again assumes the mantle following the events of "Batman R.I.P." (2008) and "Final Crisis" (2008–2009). As Batman, Dick moves to Gotham City following his mentor's apparent death and partners with the fifth Robin, Damian Wayne. On Bruce's return, both men maintained the Batman identity until 2011, when Dick returned to the Nightwing identity with DC's The New 52 continuity reboot. In a 2014 comic story, Dick is forced to abandon the Nightwing identity after being unmasked on TV and faking his death, setting up Tim Seeley's "Grayson" comic book, Dick becomes Agent 37, Batman's mole in the nefarious spy organization Spyral. Following the conclusion of the "Grayson" series, and the restoration of his secret identity in the series' final issue, Dick returns to being Nightwing as part of the DC Rebirth relaunch in 2016.