history's greatest villains (dubbed Encores) resurrected from Hell and causing chaos across time.
Ever since Superman of Earth-96.
However, as the Arrowverse's renegade outlier series, Legends of Tomorrow looks like it's playing by its own rules post-Crisis. In this week's episode, "A Head of Her Time", the Legends ventured to 1793 Versailles to find Marie Antoinette, who is the exact double of Nora Darhk. The Queen of was back from Hell and taking vengeance for her beheading by throwing an eternal party that was killing her guests. The Legends apprehended Marie, only to discover she was still beheaded - which meant tying up her headless body while keeping Antoinette's perfectly sentient head in a separate room on the Waverider. It gets even weirder: Ray excitedly showed Nora (the head of) her French doppelganger and suggested she take a 23-and-Me test because they look exactly alike. Understandably, Nora was far more disturbed that her boyfriend was showing her "a gagged, decapitated woman".
This isn't the first time a Legends of Tomorrow character ran into a historical figure who is their doppelganger. Last season, John Constantine (Matt Ryan) met his ancestor King Konstantyne in 55 B.C., but their resemblance was easily explained by them sharing a bloodline (and it was convenient for Matt Ryan to play both characters). However, Nora, who is the magical daughter of Damien Darhk (Neal McDonough) and currently the Fairy Godmother, has not been purported to have a French or Viennese heritage that ties her to Marie Antoinette. Incidentally, Damien also battled his double, in the form of his younger self, in Cold War-era East Berlin during Legends of Tomorrow season 3.
Barring some kind of timeline-altering chicanery on Grigori Rasputin. So, it's possible an explanation for how Marie Antoinette looks exactly like Nora Darhk is on the way in a future episode of Legends of Tomorrow when Nora is back on the Waverider and the former Queen of meets the Fairy God Nora face-to-face.
DC's Legends of Tomorrow airs Tuesdays @ 9pm on The CW.