Last year, when ‘Arrow’ and ‘The Flash’ crossed over, there were certain story elements that tied them together, but the episodes essentially stood on their own. This year, though, the shows will be tying together in a two-part story which will set up The CW’s upcoming third DC super hero series ‘Legends of Tomorrow’.  There aren’t any plot details available, beyond the fact that the episodes will feature nine costumed heroes joining together against a major threat.  What villain could warrant these heroes combining their might?  Zoom maybe?  But he will most likely be a season-long threat, so perhaps not.  Another candidate could be Vandal Savage (Casper Crump), who will be the Big Bad on ‘Legends’ when it premiers next year.  Considering that some members of that show’s cast are popping up during the crossover lends credence to that idea.

Executive producer Marc Guggenheim tweeted a group photo, featuring seven super heroes and pointed out that the big mashup is just three weeks away.  Check it out below:

Here is a closer look at the photo:

As you can see, the heroes pictured are ‘Arrow’ regulars Speedy, Green Arrow, Black Canary and Diggle the helmeted wonder.  The Flash stands front and center and they are joined by newcomers Ciara Renée as Hawkgirl/Kendra Saunders and Falk Henschel and Hawkman/Carter Hall.

Stephen Amell previously stated that the crossover would feature nine heroes, though so two are unaccounted for.  Caity Lotz’s White Canary would be an easy fit and since Felicity is searching for Ray Palmer, who returns as The A.T.O.M. in ‘Legends’, he could also be a pretty likely candidate.  Then again, there’s also Firestorm, technically two men, who are also part of the ‘Legends’ team.  And new character Curtis is based on a DC hero as well, Michael Holt a.k.a. Mister Terrific.  Will viewers get to see his ascension to a super identity?

More info on the crossover as it emerges.  What would you like to see happen when Ollie and Barry cross paths again?