The CW has released the first image of the crossover episode between "The Flash" and "Arrow."

The new image shows a number of Justice League members who have been assembled for the two-episode event. The episodes are supposed to also introduce new characters who will eventually be in the upcoming spin-off series "Legends of Tomorrow."

The image was shared by Marc Guggenheim, the executive producer of "Arrow" and "Legends of Tomorrow," on Twitter.

The upcoming episode is expected to see the Green Arrow, the Flash and their allies fight against Vandal Savage, the immortal caveman who will ultimately become the big villain in "Legends of Tomorrow."

Among the "Legends of Tomorrow" stars who will show up in the episodes are Franz Drameh (Firestorm II), Caity Lotz (White Canary) and Brandon Routh (The Atom). All of these characters have already been shown in "The Flash" and "Arrow" as cameos, as The CW hopes to connect the series.

In many ways, the network is trying to create its very own comic book universe on TV, the way that Marvel has in the cinemas. For the most part, the plan has worked well.

"The Flash" is currently in its second season and has scored rave reviews. The series stars Grant Gustin as Barry Allen and Candice Patton as Iris West. The show tells the story of Allen, who uses his powers to fight crime in Central City.

Meanwhile, "Arrow" is now in its fourth season and stars Stephen Amell as Oliver Queen and Katie Cassidy as Laurel Lance. The show tells the story of billionaire playboy Queen, who is determined to clean up the city as a hooded vigilante armed with a bow.

"Legends of Tomorrow" will premiere in January. "Arrow" airs on Wednesdays at 8 p.m. ET, while "The Flash" airs on Tuesdays at 8 p.m. ET on The CW.