Supergirl Flash Clip, Carter Guest Star

Following the promos and photos, DC Entertainment has released a behind-the-scenes featurette for CBS’ upcoming “Supergirl” episode which sees Grant Gustin’s Barry Allen from The CW’s “The Flash” crossing over to that show.

In the episode, which airs Monday, Kara (Melissa Benoist) gains a new ally when the lightning-fast superhero The Flash (Grant Gustin) suddenly appears from an alternate universe and helps her battle Siobhan, aka Silver Banshee, and Livewire in exchange for her help in finding a way to return him home.

In related news, executive producers Andrew Kreisberg and Greg Berlanti have reportedly let slip (via EW) that they’re getting “Wonder Woman” Lynda Carter to guest star on the show sometime next season and in a key role – as the president of the United States.

The plan was to get her to guest star in the first season, but scheduling conflicts prevented that from happening. They’re sticking with the plan though and so later this year we may get to see this possibility.

The “Supergirl” crossover episode airs next week.