The Arrowverse's epic Crisis on Earth-X crossover has kicked off with two strong episodes that delivered on the action and the excitement the shows' producers promised. Although the bulk of the first part of the event focused on the heroes from all four CW shows interacting as they gathered for Barry Allen and Iris West's wedding, the evil Nazi doppelganger superheroes made their presence felt when they invaded from Earth-X, with the Dark Arrow, Overgirl and the Dark Flash leading the charge.
But it turns out that the reason these evil versions of our favorite superheroes invaded Earth-1 wasn't to as simple as a desire to expand their nefarious reach and take control of a new world. The impetus behind the invasion was actually much simpler, and far more understandable, than that.
Overgirl, Kara Zor-El's evil double, doesn't have long to live. She is dying, as a result of overexposure to solar radiation. Thus, the Nazi villains have arrived on Earth-1 with the goal of acquiring Supergirl's heart in order to save Overgirl's life.
Non-DC Comics reading viewers and fans might wonder how it could be possible for someone as powerful as Supergirl, a Kryptonian who is powered by the yellow sun, to find herself dying due to the sun's rays, but this development should actually sound familiar to comic book fans. In fact, this is essentially a twisted take on the opening beat of the modern classic by Grant Morrison and Frank Quitely, All-Star Superman.
In the comic, which takes place outside of the main DC Comics continuity, a team of astronauts on a scientific mission to explore the sun are sabotaged by Lex Luthor. To save their lives, Superman has no choice but to travel inside the sun itself, essentially overwhelming his cells with solar radiation.
As a result, Superman found himself with only one year to live, the beginning of a brilliant story that explored Superman like few others. All-Star Superman is seen by many as a quintessential Superman story that every fan should read, and it seems like the Arrowverse has found a small way to honor the comic series' legacy. Since it's unlikely that Supergirl would face death on her own titular series, having Overgirl be the one to suffer the effects of excess solar radiation allows the Arrowverse to borrow a page from a popular comic book series without sacrificing one of its main characters.
We do wonder, though, who might be responsible for Overgirl's condition. Could it be Earth-X's version of Lex Luthor -- who has yet to appear in the Arrowverse -- or someone else entirely? Perhaps a Freedom Fighter who is a part of the now-deceased Guardian's team of rebels? Hopefully we'll get an answer to that before Crisis on Earth-X concludes... or perhaps even in a follow-up storyline somewhere down the line.