This week marks the return of The Flash and Arrow to The CW, with the network's latest superhero addition, Supergirl, debuting next week, along with Legends of Tomorrow. Later this season, all these characters will be featured in a four-show crossover, which is currently in production. Over the weekend, Legends of Tomorrow star Caity Lotz shared a new set photo with Supergirl herself, Melissa Benoist.

Caity Lotz debuted the photo on Twitter, along with the caption "Seriously Super." Last week, Arrow star Stephen Amell shared a number of photos, with production continuing this weekend. No plot details have been released for this crossover, but The CW did release a new Superhero Fight Club trailer with stars of all four shows. It's unclear whether or not the Superhero Fight Club will ever figure into the plot of any CW show, or this crossover episode, but we know there will actually be two crossovers featuring Supergirl.

The four-part crossover that will involve each show will air in late fall, but both The Flash and Supergirl stars will be featured in a separate musical crossover. The executive producer teased that he wanted to take advantage of the fact that several stars from both shows boast exceptional singing voices. Both Grant Gustin and Melissa Benoist had been featured in singing roles in Fox's hit series Glee before tackling their superhero roles.

Related: Jon Cryer as Lex Luthor Revealed in Supergirl Season 4

In Season One, Supergirl soared fighting crime and battling various villains, chief among them two Kryptonians who were intent on destroying earth, but she has yet to find that same empowerment as Kara Danvers. In The CW's Supergirl Season Two, Kara has left the safety of being Cat Grant's assistant in order to figure out what she really wants to do, while as Supergirl she continues to work at the DEO, protecting the citizens of National City and searching for Jeremiah and Cadmus. Along the way, she will team up with Superman (Tyler Hoechlin) to battle new villains, as she strives to balance her personal life with her life as a superhero.

Supergirl will be introducing a number of new characters this season, including Lynda Carter, the original Wonder Woman, as the President of the United States. Floriana Lima has also signed on to play Maggie Sawyer, the first ever openly gay comic book character, along with Katie McGrath as Lena Luthor. The CW Network show is also introducing Maggie Sawyer's girlfriend Kate Kane (Batwoman), and Barbara Gordon (Oracle), although they haven't been cast yet. Take a look at this new Supergirl set photo below.

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