"Supergirl" episode 18, "Worlds Finest," will have Barry Allen aka The Flash (Grant Gustin) appearing on the show despite "Supergirl" appearing on CBS and "The Flash" coming from The CW. Fans have now begun asking if this can happen the other way around, and producer Greg Berlanti has finally responded in an interview with The Hollywood Reporter.

"We would love that. We're waiting to see the audience reaction from something like this," Berlanti explained. It is likely that this means that something is indeed in the works but the studios are still waiting to see how well the crossover is received by critics and fans.

If this were to happen, it is likely Supergirl will travel to the universe of "The Flash" in order to help the Barry Allen in his fight against Zoom (Teddy Sears).

Berlanti also explained why Stephen Amell, who plays the Green Arrow in "Arrow," was not included in the crossover. According to Berlanti, The Flash is the key to the whole event given that The Flash is the one capable of traveling through different timelines and realities and the studios had to wait for "The Flash" to establish the story involving the multi-verse.

It was also explained that "The Flash" and "Supergirl" have a similar tone while "Arrow" is marketed as a darker, more mature show with more violence and grim events taking place. With similar tones, it is explained that putting the two superheroes together was less of a challenge, narrative-wise.

The producer also reiterated how difficult it was to get the crossover to even happen. Although "Supergirl" and "The Flash" are produced by the same studio, they appear on two different networks, with the former on CBS and the latter on The CW. 

"Supergirl" episode 18 will air tonight on CBS while "The Flash" season 2 continues this March 29 with the episode "Flash Back."