You'd be hard pressed to find two superheroes in the DC television universe who are happier to be saving lives than Barry Allen (Grant Gustin) and Kara Zor-El (Melissa Benoist).

Even though they've both faced tough hardships on their respective shows this season, the two will bring out the plucky optimism in each other when The Flash makes his way to National City on Monday's Supergirl.

Supergirl bosses explain how crossover episode is more than a gimmick

"It's so exciting and pure fun to watch those two characters together," Benoist tells TVGuide.com. "There's this healthy rivalry. They're allies. Both of them are happy to be superheroes and to help people. It's kind of infectious to watch them do it together."

Fans will have the chance to see exactly how that plays out when the Supergirl and The Flash crossover airs Monday at 8/7c on CBS.

(Full disclosure: TVGuide.com is owned by CBS)