Who is the fastest person alive? CBS has released new details and a poster from their upcoming Supergirl crossover episode with The Flash. 

The episode premieres on March 28th at 8 p.m. ET/PT on CBS.

From CBS:

“Worlds Finest” – Kara gains a new ally when the lightning-fast superhero The Flash (Grant Gustin)
suddenly appears from an alternate universe and helps Kara battle Siobhan, aka Silver Banshee, and Livewire in exchange for her help in finding a way to return him home, on SUPERGIRL, Monday, March 28 (8:00-9:00 PM, ET/PT) on the CBS Television Network. Grant Gustin crosses over as The Flash.”

Check out the poster for the big crossover episode:

What do you think? Do you watch both Supergirl and The Flash? Are you excited for the crossover episode? What other superhero shows would you like to see do a crossover?