Flash Supergirl crossover
The Flash and Supergirl crossover is happening at CBSThe CW/ CBS

After months of speculation, The Flash and Supergirl crossover has been confirmed by CBS. Central City's Scarlet Speedster Barry Allen will travel to Kara Danvers' National City in a special mash-up episode airing on 28 March on CBS.

The Flash and Supergirl executive producers Greg Berlanti and Andrew Kreisberg said in a statement: "We are so incredibly excited to announce something that we have dreamed of happening since we starting making Supergirl — The Flash and Supergirl are teaming up!"

"We want to thank Grant Gustin for making the time to come visit (on top of his already immense workload) and all of the folks at CBS, The CW, Warner Bros. and DC for working this out. And finally thanks to the fans and journalists who have kept asking for this to happen. It is our pleasure and hope to create an episode worthy of everyone's enthusiasm and support," they shared.

Grant Gustin, who plays Flash in The CW series, also shared his excitement via Twitter. He wrote: "Secret is out. Melissa Benoist and I are gonna get to have some fun on Supergirl together."

Warning: Spoilers ahead

In another Instagram post, Gustin shared the episode script, thereby revealing the title. The crossover will happen in episode 18 of Supergirl, which is titled Worlds Finest.

The episode title gives the fan little details about the plot. Comic Book speculated that one noteworthy aspect about this title, besides the obvious reference to the iconic comic series, is the lack of apostrophe on "Worlds". implying The Flash and Supergirl come from different worlds and are the finest of their respective worlds. So, a multiple universe plot may come into play.

World's Finest was the name of a comic book series that DC ran back in 1941, mainly featuring Batman and Superman. Supergirl airs every Monday at 8pm EST on CBS. The Flash season 2 airs on Tuesdays at 8pm EST on The CW.

Really really. Flash is about to meet Supergirl. @melissabenoist

A photo posted by Grant Gustin (@grantgust) on