The Flash speeds his way onto Monday night’s “Supergirl” on CBS, where he’ll help out Kara as she battles two villains – Silver Banshee and Livewire.

“We’ve been setting up Silver Banshee for a bunch of episodes,” Executive Producer Andrew Kreisberg told reporters on Thursday after a screening of the episode, as he addressed why those two characters were targeted as Supergirl/Flash foes for the crossover episode.

“That was actually a lot of fun to be able to bring on Italia [Ricci] and establish her as Siobhan, because a lot of times, you know… our shows tend to be so much about the heroes and so much about the heroes’ internal lives that the villains tend to get short shrift, and it was a real opportunity for us to introduce a character and to have them really stay on the show for a while and really kind of get to know them and maybe even like them a little bit so that when they did transform, it actually meant something as opposed to ‘just the crazy thing that happens at the end of act one,'” he continued. “For our money, we thought Livewire was one of our most successful villains from early on, so we were very much interested in bringing her back and if you were going to have two heroes, you’re going to want to have multiple villains. An early version of the story actually had Bizarro teaming up with them as well and it was going to be three against two, but it proved to be financially irresponsible, so we stuck with the two.”

The setup for why Grant Gustin’s character enters another

multiverse where Melissa Benoist’s Supergirl lives, won’t actually air until

the day after the crossover on Tuesday’s episode of “The Flash” on

The CW.

“They kind of flip order obviously because this will

air Monday and ‘The Flash’ one that sort of hints at how he gets over there and

gets back airs on Tuesday,” Executive Producer Greg Berlanti said at the

same screening. “So the audience has to forgive us that one is going to actually air before the other and they shouldn’t wait to watch ‘Supergirl’ until after

‘The Flash’ episode. They should certainly watch it before, but you’ll see the

shout out in the episode. It deals with Barry increasing his speed and I’m very

excited about next week’s episode of The Flash too.”

Grant’s character, the generally upbeat Barry Allen, whose

show, “The Flash,” has been dealing with the multiverse concept throughout

Season 2, was — thanks to his speed — the perfect character to cross over. Berlanti noted that “in

a perfect world, it probably would have been both of them,” coming to

“Supergirl” though, referring to The Flash and Stephen Amell’s

“Arrow” character Oliver Queen/The Green Arrow.

But, “logistically, that would have been a nightmare at

this point in the year to try and do it to both shows, so we had to kind of

facilitate one,” he added about trying to schedule such an epic event.

And while it won’t happen this season, producers are open to

crossing Kara over to “The Flash.”

“We would love that, just like we loved this and we’re excited by this,” Berlanti said. “I think

we want to wait and see the audience’s reaction to this, but just as

storytellers and as fans and fans of the actors, honestly. We love it when we

can figure out a way creatively to do it and hopefully everybody enjoys it.”

Unconnected to the crossover episode, in response to one

reporter’s question at the screening about how they have cast so many actors

from previous “Supergirl” and “Superman”-related TV and

film projects, producers revealed that they approached “Wonder Woman”

star Lynda Carter to appear in their CBS show.

“We had the perfect role for Lynda Carter and we

couldn’t work out her schedule,” Berlanti said.

Kreisberg chimed in suggesting they’ll bring her on next

year.

“She’s the female President of the United States,”

Berlanti revealed of the character they hope to one day get Lynda to play.

The “Supergirl” episode featuring Grant Gustin as

his “The Flash” character Barry Allen airs Monday at 8/7c on CBS.

“The Flash” airs Tuesday at 8/7c on The CW.

— Jolie Lash