When Arrow first hit our screens back in 2012, no one expected it to become quite as successful as it did. However, three years on and it's cemented itself in comic-book history, becoming one of the most successful on screen superhero adaptations yet and spawning an equally popular spin off title.
Back during the first season, the show was very grounded, acting almost like it was trying to be a budget Batman. However, following the introduction of The Flash, Ra's al Ghul, The League of Assassins and the upcoming Legends of Tomorrow, the game has certainly changed. With the potential to include resurrection, metahumans and mysticism into the universe, the possibility for introducing more characters has become much greater. Fan favorite, John Constantine will be making an appearance later this season in Arrow and the time traveller, Rip Hunter, is set to play a lead role in [DC's Legends of Tomorrow](tag:2937021) next year.
But why stop there? Even with Batman and Superman sadly off the cards due to licensing, DC has a huge back catalogue of other heroes that would feel right at home in the Arrowverse.
Now technically, this one's cheating a little bit as Vixen already exists in the Arrowverse. However, she's yet to be seen in live action, with her only appearance so far being in the canon animated series Vixen.
To those who aren't avid readers of DC comics, Vixen may come off as a rather obscure character. However, she has every right to make it to the big leagues. Vixen has the ability to mimic any animal that has ever existed on Earth, making her a massive threat to any metahuman that she happens to meet.
Of all the heroes and villains on this list, Vixen is the most likely to make a future appearance. Her animated series, featuring the voice work of several Arrowverse stars, is technically already part of the continuity and the folks at DC have hinted on more than one occasion that a live action series may be in the works.
If not, there's always going to be space with the Legends of Tomorrow, and her already established relationship with Green Arrow and The Flash makes it all the more likely.
6. Bart Allen
Bart Allen is the great grandson of Barry Allen A.K.A. The Flash and has appeared in the comics as The Flash's sidekick, Impulse, the second Kid Flash and the fourth Flash. With time travel now playing a huge part in the story of The Flash, it's very possible for Bart Allen to make a fleeting appearance some time soon and maybe a more regular role in seasons to come.
With Jay Garrick now a series regular and Wally West pencilled in for later this season, including Bart doesn't seem like much of a long shot for The Flash. The existence of multiple speedsters and time travel was established duirng the first season and with Barry's team ever-growing, there'll always be space for Impulse.
5. Talia al Ghul
With Ra's al Ghul vanquished and Malcolm Merlyn leading the League of Assassins, infighting within the organisation is highly likely at some point. Ra's' other daughter, Nyssa, made it clear she had no respect for Merlyn but it's evident she has no way of overthrowing him without the outcome ending in her own death.
Enter Talia al Ghul, Nyssa's estranged sister. Such a dangerous pairing would be enough to topple Merlyn from his throne and establish a wider universe at the same time. During S02E02 of The Flash, Sand Demon's Earth-1 counterpart informed Detective Lance that he had been in Blackgate Penitentiary when the accelerator had exploded, confirming there's a version of Gotham City in the Arrowverse. Introducing Talia could be the first step to introducing more of the Caped Crusader's gallery of rogues.
Additionally, Talia would bring a new dynamic into the fold. Without Batman in the mix, Talia would have no clear intentions and would act as a serious wildcard should Oliver come into contact with her. While Nyssa represents the orde of the League, Talia could take on the role of an unpredictable killer, possibly acting as the lead villain in a later season.
4. Booster Gold
Whenever fans like to speculate on who may be appearing next in Arrow or The Flash, a list is never complete without the inclusion of Booster Gold. Born in the 25th Century, Michael Jon Carter possessed no superhuman powers, however he was particularly knowledgeable on 20th and 21st Century events and was a superb athlete. As a result, he became a valuable asset to the Justice League.
Booster Gold is far more likely to appear in Legends of Tomorrow than in any other series due to his relationship with Rip Hunter and time travel in general. He's unique in that unlike the heroes we've already met, he has no issue with the public knowing who he is and thrives on popularity, becoming an actor and all round celebrity during his time as a superhero. Introducing this new dynamic to the team would definitely succeed in changing up the game and contrast heavily against Oliver Queen's dark and shadowy persona.
3. Blue Beetle
Much like The Flash and Green Lantern, the title of Blue Beetle does not refer to just one person. Blue Beetle has in fact been three heroes during his existence, however for the purposes of this list I'll be referring to the most recent iteration: Jaime Reyes.
Reyes is a teenage superhero of Mexican/American descent who uses a powerful exoskeleton to fight crime. He's been both a member of the Justice League International and Teen Titans, meaning a potential crossover with the upcoming Titans TV series makes Blue Beetle's chances even better.
Despite being a fan favorite, Blue Beetle has had very little screen time, appearing briefly in Season 10 of Smallville. Fortunately, he fits right into the new direction the Arrowverse is taking, with alien origins and over-the-top abilities that would feel right at home in The Flash or Legends of Tomorrow.
Nightwing A.K.A. Dick Grayson is already set to lead TNT's Titans in the near future and so far, the showrunners haven't ruled out a crossover between their new show and the Arrowverse. However, for Nightwing to have his own standalone arc in an episode of Arrow would be perfect, as he follows a very similar lifestyle to Oliver Queen in the comics.
Thanks to Blüdhaven already existing within the Arrowverse, incorporating Nightwing into the franchise without requiring a Batman-centric back story won't be hard. Nightwing could easily appear in the next season of Arrow briefly to advertise Titans and could pave the way to an even larger shared universe.
And due to his similarity to Batman, he could easily fill in should the creators feel the need to create a Justice League team up movie. It's a minor, probably unnecessary point, but it's fun to think about, right?
Aside from being easy to write in, Nightwing would provide some much neede fan service and bring in more viewers who may not have been as familiar with the likes of Green Arrow and Black Canary. In bridging the gap between the hard line Oliver Queen and the quip-fueled Barry Allen, Nightwing complements both characters perfectly and wouldn't look out of place in a future crossover episode.
1. Black Flash
What happens when you're so fast, not even Death itself can catch you? The Black Flash is the embodiment of Death to those connected to the Speed Force. Black Flash will only appear to speedsters and his presence will always result in the death of a hero. With few exceptions, there is no escaping it.
Upon seeing him in The Flash battling Jay Garrick, many assumed that Zoom would take on the role of Black Flash in the series. However, Zoom already exists as a character himself and despite the suit and the speed, has very little in common with the Black Flash. As a speedster, even Zoom isn't immune to the touch of Black Flash.
Introducing Black Flash as a primary villain in a future series of The Flash could see our hero having to team up with every speedster, good or bad, to try and take him down. By including it, you can be sure many of our favorite characters won't make it to the end of the series alive, but for a villain so terrifying, it'll almost be worth it.
To date, Bart Allen is the only speedster to have evaded the Black Flash by running to the end of time itself. At this stage in the TV show, Barry is still relatively inexperienced, potentially making the Black Flash one of the Scarlett Speedster's most challenging villains yet to appear.