John Wesley Shipp and Stephen Amell Are The Flash in "Elseworlds" BTS Photo

In a bizarre twist of fate, it is Stephen Amell and not Grant Gustin who gets to stand side-by-side with John Wesley Shipp in nearly-identical Flash costumes for the first time.

The pair stopped to share a photo together during filming on the "Elseworlds" crossover, which sees Oliver Queen and Barry Allen switch places, with Amell becoming The Flash and Grant Gustin becoming Green Arrow.

Besides Superman, Supergirl, Lois Lane, Batwoman, and more, the pair will get to work with Shipp's classic '90s Flash. Amell has been elated about working with Shipp for hours, sharing enthusiastically and praising Shipp.

"What an absolute honor it was to work with John Wesley Shipp today," Amell had tweeted just before. "90’s Flash Lives!!"

Shipp first played Barry Allen/The Flash on TV for a single season beginning in 1990. Years later, he returned to The Flash when the show was revived on The CW. This time around, he played Henry Allen, Barry's father. After Henry's death at the hands of Zoom, it was revealed that Henry's Earth-3 doppelganger was in fact Jay Garrick, the "Golden Age" Flash from the comics, giving Shipp another chance to ride the lightning.

Garrick has appeared rarely since he was revealed, and given the mystery surrounding "Elseworlds," it is impossible to know whether Shipp is playing his version of Barry Allen, the Jay Garrick we saw previously, or something else entirely.

In The Flash's first season, Barry Allen's first trip into the timestream provided him with glimpses of the past, future, and alternate Earths -- including one where Shipp's Barry Allen was wearing the classic costume from the 1990 series.

While the plot of "Elseworlds" remains a bit of a mystery -- and arguably gets more confusing by the day -- we do know that it will see Supergirl, The Flash (Grant Gustin), and Green Arrow(Stephen Amell) crossing paths with a wide array of DC Comics characters.

In addition to Superman and Lois, the event will include the live-action debut of Kate Kane/Batwoman (Ruby Rose) as well as appearances from Dr. John Deegan (Jeremy Davies), The Monitor (LaMonica Garrett), and Nora Fries (Cassandra Jean Amell).

"The crossover is f---ing bananas," Amell explained during a recent Facebook Live. "It's crazy... I think that this will be the best crossover event that we do. And not just the best but the best by a really, really wide margin. And I think that last year was fantastic."

The three-night "Elseworlds" event will begin with Supergirl on Sunday, December 9th, before carrying over to December 10th's Arrow and December 11's The Flash.