The logistics of getting Supergirl to interact with Arrow or The Flash are never easy, but fans have often wondered if the “Earth-1” we follow has a doppelganger Kara Zor-El out there, or if Supergirl’s universe might have an Oliver Queen to facilitate easier appearances. Sadly, producers have shot down that particular brand of crossover, citing the “floodgates of insanity” it might open.

To bring you up to speed, typically only The Flash interacts with alternate-universe doppelgängers from Earth-2 (or H.R.’s Earth-19), given Barry’s ability to leap dimensions. Last year’s “Welcome to Earth-2” had its fun with alternate versions of Arrow-verse characters, though Barry’s trip to Supergirl’s Earth-38 (then on CBS) specifically pointed out the lack of shared characters like Green Arrow, Caitlin Snow or Cisco Ramon.

Producers have even entertained the notion of who an Earth-1 Kara Zor-El might represent (their world is comparatively devoid of aliens), but it’s worth wondering if ever any unseen doppelgängers could appear on the respective series, if only for a fun cameo. After all, there’s no reason Earth-38 couldn’t have a non-vigilante Mayor Queen, or that James Olsen couldn’t appear as a respected Earth-1 journalist, absent any Super-pals, right?

Sadly, as executive producer Andrew Kreisberg put it (via TVLine), too many complications arise from introducing such counterparts, especially without the opportunity to explore them in-depth:

The producers have discussed seeing the doppelgängers, but “the problem with that is if we do that once, we’re going to open the floodgates of insanity,” Kreisberg says, adding that there would have to be “a really good story” for such an appearance.

In fact, we’ve even seen the idea nixed once before, as the four-way “Invasion!” crossover almost introduced Lynda Carter’s Earth-1 Olivia Marsdin, who at the end of the three-part event would have succeeded the Presidency to match her Earth-38 counterpart. Producers ultimately abandoned the idea after a studio note deemed it “too confusing” and “one sci-fi problem too much.”

It’s too early to know what next brings together Supergirl, Flash, Arrow and Legends of Tomorrow (did someone say Black Lightning?), but do producers have a point about alternate-universe doppelgängers over-complicating matters? Is it unreasonable to imagine ever combining universes, to eliminate this question altogether?

In the meantime, The Flash and Supergirl will next come together for a musical “Duet” in March, so stay tuned.

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