The Flash speeds his way onto Supergirl on CBS on Monday, where he'll help out Kara as she battles two villains, namely Silver Banshee and Livewire.

"We've been setting up Silver Banshee for a bunch of episodes," Executive Producer Andrew Kreisberg said 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."

Moreover, 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 actress 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.

Tags: Supergirl CBS Lynda Carter