Yesterday, Arrow and The Flash executive producer Marc Guggenheim revealed the first photo from the highly-anticipated crossover event for both shows, which will take place in just three weeks. Today, a new poster has surfaced, courtesy of Comic Book Movie, which promotes a fan screening of the two-episode event entitled Legends of Yesterday. The poster features Arrow star Stephen Amell fighting alongside The Flash star Grant Gustin, with the new tagline "Heroes Join Forces." The fan screening is being held by AT&T, with more information to come later on where and when this event will take place.

You may recall that last season's crossover event pitted these two heroes against each other, but that will not be the case this year. Stephen Amell recently revealed that both Flash and Arrow will be fighting a common enemy together, who is believed to be Casper Crump's Vandal Savage, one of the villainous characters from The CW's upcoming spinoff DC's Legends of Tomorrow. Since the crossover event is called Legends of Yesterday, expect both of these episodes to set the table for this spinoff, while bringing characters from Star City and Central City together.

Yesterday's photo featured Arrow's Oliver Queen (Stephen Amell), Thea Queen (Willa Holland), Laurel Lance (Katie Cassidy) and Diggle (David Ramsey), alongside The Flash himself, Barry Allen (Grant Gustin) and DC's Legends of Tomorrow stars Hawkman (Falk Hentschel) and Hawkgirl (Ciara Renee). It is also believed that another DC's Legends of Tomorrow star, Brandon Routh (Atom) will surface in this episode. Ray has been missing and presumed dead ever since the last season of Arrow, and we know he will return for DC's Legends of Tomorrow.

Related: Supergirl, Flash & Arrow Team Up in The CW's Superhero Sizzle Reel

We have previously seen Ciara Renee's Hawkgirl on the Season 1 finale of The Flash, and she surfaced again in last week's episode, The Darkness and the Light. It isn't known if we'll see Hawkgirl between now and the crossover episode, but it's possible that will be the first time we see her in the full Hawkgirl costume. We'll have to wait and see if Hawkman surfaces on either show before the two-part episode.

Unfortunately, The CW hasn't released any official plot details for this event, which kicks off with a new episode of The Flash on Tuesday, December 1, followed by Arrow on Wednesday, December 2. We'll keep you posted as soon as we learn more about what is shaping up to be one of the most highly-anticipated events of the new TV season. Are you looking forward to seeing Barry and Oliver fighting side by side against a common enemy? Let us know what you think after checking out this poster.

<strong><em>Arrow</em></strong> Flash Crossover Poster