Flash-Supergirl crossover
Melissa Benoist as Supergirl and Grant Gustin as The FlashThe CW/CBS

The much awaited The Flash and Supergirl crossover event is just two weeks away. Actor Melissa Benoist and executive producers Greg Berlanti and Ali Adler have shared some new details about Barry Allen and Kara Danvers's mash-up episode.

The first poster released for the episode teased a race between the Superman's cousin and the Speedster. At the Paley Fest, Benoist said: "I'm excited for you guys to see the race." In the episode, Barry will be stranded in Kara's National City, which will exist in an alternate timeline.

Benoist said the hour-long event is "upbeat and happy". She explained: "It is the most joyous occasion to have these two superheroes together in the same place, at the same time, working together. They are both so happy with their powers and what they get to do and how they get to help people, that it's kind of infectious and exciting and upbeat and happy."

To watch the crossover, fans don't have to follow every episode of the CBS and The CW show, said Berlanti. He told TVLine: "Obviously, you have to understand the concept of superheroes and that they can have all sorts of different kinds of powers when [The Flash] shows up. People will appreciate how he [Barry] gets [to National City] and their journey that they take in the hour."

According to Adler, although the two heroes will enjoy "quite an adorable banter" and will "immediately click", but their friendship will make James Olsen (played by Mehcad Brooks) jealous.

Olsen is currently single and is interested in Kara, and Barry's arrival may ruin his chance with the Supergirl. Brooks said: "We have this little rivalry, because he's a superhero, too, and kind of hitting on my girl a little bit. I'm like, 'Damn you, Barry'."

The crossover will happen in Supergirl's episode 17 titled Worlds Finest and will air 28 March on CBS. Trailer for the crossover is expected to be released soon.