CW Universe

Arrow
The series takes a realistic look at the Green Arrow character, as well as other characters from the DC Comics universe. Although Oliver Queen/Green Arrow had been featured in the television series Smallville from 2006 to 2011, the producers decided to start clean and find a new actor (Amell) to portray the character. Arrow focuses on the humanity of Oliver Queen, and how he was changed by time spent shipwrecked on an island. Most episodes have flashback scenes to the five years in which Oliver was missing. Arrow has received generally positive reviews from critics, and was the CW's highest-rated new series in five years. The series averaged about 3.68 million viewers over the course of the first season, and has received three awards and multiple nominations. To promote it, a preview comic book was released before the television series began, while webisodes featuring a product tie-in with Bose were developed for the second season. The first and second seasons are available on DVD and Blu-ray in regions 1, 2 and 4; a soundtrack was also released for the first two seasons. The third season premiered on October 8, 2014, with a spin-off series set in the same universe, titled The Flash, that aired on October 7, 2014. On January 11, 2015, Arrow was renewed for a 23-episode fourth season.

The Flash
Initially envisioned as a backdoor pilot, the positive reception Gustin received during two appearances as Barry on Arrow led to executives choosing to develop a full pilot to make use of a larger budget and help flesh out Barry's world in more detail. Colleen Atwood, costume designer for Arrow, was brought in to design the Flash's suit, which was modeled after the comic books. The creative team wanted to make sure that the Flash would resemble his comic book counterpart, and not simply be a poor imitation. The series is primarily filmed in Vancouver, British Columbia, Canada. The Flash premiered in North America on October 7, 2014, where the pilot became the second-most watched premiere in the history of The CW, after The Vampire Diaries in 2009. It has received generally positive reviews from critics, and won the People's Choice Award for "Favorite New TV Drama" in 2014. On January 11, 2015, The CW renewed The Flash for a second season.[1]

Legends of Tomorrow
In January 2015, Berlanti stated that there were "very early" preliminary talks for an additional spin-off series centered on Ray Palmer / The Atom (Brandon Routh).[116] In February 2015, it was reported that a spin-off series, which is described as a superhero team-up show, was in discussion by The CW for a possible 2015-16 midseason release. Berlanti and Kreisberg would executive produce alongside Guggenheim and Sarah Schechter. The potential series would be headlined by several recurring characters from both Arrow and The Flash, including Ray Palmer, Leonard Snart (Wentworth Miller), Dr. Martin Stein (Victor Garber) and Heat Wave (Dominic Purcell). Caity Lotz is also mentioned to be among the main cast. There is potential for other Arrow/Flash characters to cross over to the new series. In March 2015, Amell confirmed the series would air in the 2015–16 midseason. Additionally, Kreisberg stated more would be revealed about the nature of the series by the end of Arrow '​s third season, specifically why Lotz is slated to appear, given her previous character, Canary, was killed at the start of season three.[119] Berlanti also stated there was a particular reason for the other half of Firestorm, as seen on The Flash, Ronnie Raymond (Robbie Amell) not being mentioned in the initial cast announcement.[120] Blake Neely will once again serve as composer for the series.

Vixen
In January 2015, the CW announced that an animated web-series featuring the DC heroine Vixen would be debuting on CW Seed in late 2015. It will be set in the universe of Arrow and The Flash. It was later revealed that Megalyn Echikunwoke would voice Vixen and that Stephen Amell, Grant Gustin, Emily Bett Rickards, and Carlos Valdes Would all reprize their characters.

Constantine (TV Series)
By May 2015, Amell had had discussions with DC Entertainment about portraying Queen on Constantine, saying, "The reason that I was going to guest star on Constantine...was [Constantine's] an expert when it comes to the Lazarus Pit, which is now something that is a part of and will continue to be a part of Arrow." Amell stated that, even though Constantine was not renewed for a second season, a crossover "was and is still on the table". Guggenheim revealed a desire to integrate Constantine into the Arrowverse, saying, "A lot of the pieces are in place, except for that one final piece, which is what’s the fate of Constantine? That’s the tricky thing. But it comes up in the writers’ room constantly — we have a number of ideas, one idea that’s particularly exciting to me. We’re in a little bit of a wait-and-see mode". In July 2015, Mericle added on the subject, "It's something we've been talking to DC about and it's just a question of some political things, but also [Ryan]'s schedule."

In August 2015, it was confirmed that Ryan would appear in Arrow's fourth season episode "Haunted" for a "one-time-only-deal". Guggenheim said, "This is something the fans were clamoring for," praising DC for being so "magnanimous and generous in giving us this one-time dispensation." Due to Arrow and Constantine sharing the same studio, the producers of Arrow were able to use Ryan's original outfits: "The trench coat, the tie, the shirt...the whole wardrobe is being taken out for [sic] storage and shipped up to Vancouver [where Arrow shoots]." John Badham, a director on Constantine, directed the episode that Constantine appears in.[73] Mericle confirmed that this version of Constantine would be the same character that had appeared in Constantine.[74] On filming the episode, Guggenheim referred to it as "a Constantine/Arrow crossover" and felt that "we got the chance to extend Matt Ryan’s run as Constantine by at least one more hour of television. I think you’ll see he fits very neatly into our universe. It never feels forced".[75]

Supergirl
In November 2014, Berlanti expressed interest in his CBS series Supergirl existing in the same universe as Arrow and The Flash,[76] and in January 2015, The CW president Mark Pedowitz revealed that he was also open to a crossover between the series and networks. However, CBS president Nina Tassler stated that month that, "those two shows are on a different network. So I think we'll keep Supergirl to ourselves for awhile."[77] In August 2015, Tassler revealed that while there were no plans at the time to do story crossovers, the three series would have crossover promotions.[78] In January 2016, Tassler's successor Glenn Geller said "I have to be really careful what I say here" in regards to a potential Supergirl/Arrowverse crossover, so "Watch and wait and see what happens."[79]

In February 2016, it was announced that Gustin would appear on the Supergirl episode "Worlds Finest", with Berlanti and Kreisberg, also a Supergirl executive producer, thanking "the fans and journalists who have kept asking for this to happen. It is our pleasure and hope to create an episode worthy of everyone’s enthusiasm and support."[80] The crossover required "a lot more logistical trickery" than the usual Arrowverse crossovers due to Gustin filming The Flash in Vancouver alongside Arrow and Legends of Tomorrow, while Supergirl is produced in Los Angeles.[81] Gustin was optimistic that the crossover in 2016 would allow another crossover the following year with the rest of the Arrowverse shows.[82] In "Worlds Finest", Supergirl is established as being in an alternate universe where the Flash helps Kara fight the Silver Banshee and Livewire in exchange for her help in returning home.[83] The events of the episode will intersect with the events of the eighteenth episode of The Flash, set to air on April 5, 2016.