The 2019 Arrowverse crossover event, Crisis on Infinite Earths, is slowly establishing that many of the classic television series based on DC Comics' books are part of the same shared universe and are now considered canon. In this the television event is growing to resemble the comic book miniseries that inspired it, which took the dozens of realities making up DC Comics' multiverse and joined its characters together in an epic battle for the fate of all reality.
As the air-date of Crisis on Infinite Earths approaches, more and more revelations are coming to light regarding how far the producers of the Arrowverse are going to link as many DC TV shows into the event as possible, despite the difficulties in scheduling actors and the legal pitfalls involved in moving characters across production companies and rival networks. One such effort would have brought actor Cameron Cuffe, who plays Superman's grandfather Seg-El on the Syfy Channel series Krypton, into Crisis as an active participant. Unfortunately, scheduling issues prevented Cuffe from appearing in Crisis on Infinite Earths, which would've allowed Seg-El to meet three different versions of his grandson.
Rumors are running rampant as to what heroes might show up and what other shows might yet be introduced into Crisis, with the original Wonder Woman, Lynda Carter, apparently in talks to reprise her role as Diana Prince. Likewise, Burt Ward, who played Robin in the 1966 Batman series, has joined Crisis on Infinite Earths, but there's no indication of what character he is playing. And he's not the only one coming back, as there are plenty of characters from various shows making the jump to the Arrowverse.
The Flash (1990)
The road to Crisis On Infinite Earths began with the 2018 Arrowverse crossover Elseworlds. It was here that the Earth of the 1990 The Flash series, which aired for one season on CBS, was confirmed to be part of the Arrowverse and designated as Earth-90. John Wesley Shipp reprised his role as Earth-90's version of Barry Allen/The Flash, who was apparently the sole survivor after a cosmic being known as The Monitor tested the heroes of Earth-90 and found them wanting, condemning them to oblivion. Before his Earth could be completely destroyed, however, this Flash was able to run fast enough to travel between worlds and deliver a warning to the heroes of Earth-1 that their Earth would be the next to be tested.
Shipp has been confirmed as appearing in Crisis on Infinite Earths, though it is unclear what role he will play. The fate of Earth-90's Barry Allen was uncertain following Elseworlds, so it is possible he could return in that role. It is also possible that Shipp might be reprising the role of Jay Garrick, the Flash of Earth-3, who was last seen contemplating retirement in The Flash, season 4, episode 15, "Enter Flashtime." It's also possible that Shipp could be portraying an entirely different Flash from another Earth entirely; perhaps one where Dr. Henry Allen (a third role Shipp has played) became The Flash instead of his son.
It is also possible that this Barry Allen may not be the only refugee of Earth-90 to appear in Crisis on Infinite Earths. When he met the heroes of Earth-1, this Flash commented that John Diggle wasn't wearing his ring. This seemed to be a nod to a fan theory that John Diggle was Earth-1's version of Green Lantern John Stewart. The theory was seemingly confirmed later during Arrow season 7, when it was revealed that Digg's step-father had the surname Stewart. While it has yet to be confirmed that David Ramsey might appear as some version of John Diggle or John Stewart that is armed with a Green Lantern ring as part of Crisis, now would be the time if it were ever going to happen.
First airing on The CW in January 2018, Black Lightning was intentionally separated from the Arrowverse at large. This is partly because the series was originally developed for Fox and partly due to showrunner Salim Akil's desire to "create our own world" and be free of the need to coordinate with the other Arrowverse showrunners. Indeed, Akil had designs on creating his own universe, yet the show still dropped some playful references to Arrowverse heroines like Supergirl and Vixen.
Despite this, Black Lightning star Cress Williams will be appearing in Crisis on Infinite Earths as The CW's version of Jefferson Pierce/Black Lightning. However, it is unclear precisely how this version of Black Lightning will be brought into the fight and how he will react to the idea of an entire universe full of metahumans, given the relative scarcity and secretive nature of super-powered people on his Earth. The most popular theory is that Jefferson may be recruited by Oliver Queen, who it is believed will be traveling the multiverse in Arrow season 8, seeking allies to help him and The Monitor in the coming battle. After Crisis, however, it seems likely Jefferson will return home and remain on his own Earth, unless all of the CW shows are merged into one reality as a result of Crisis on Infinite Earth's ending.
While Crisis on Infinite Earth is not expected to have any sequences where animated characters will fight alongside their live-action counterparts, a la Who Framed Roger Rabbit, the DC Animated Universe will still be represented. Actor Kevin Conroy, best known as the voice of Batman in countless cartoons and video games, will be playing Bruce Wayne in Crisis on Infinite Earths, thus marking the first time that he's portrayed the character in live-action. Given that, Conroy will likely be playing an older, retired version of Batman, similar to the character he voiced in the animated series Batman Beyond.
Fans of Smallville have been clamoring for a crossover with the Arrowverse for years and it seems they are finally getting their wish. Both Tom Welling and Erica Durance, who played Clark Kent and Lois Lane in the long-running Superman prequel, have been signed to reprise their roles for Crisis on Infinite Earths. It is unlikely they'll be sticking around in the Arrowverse after the event, however, given their commitment to other projects and Michael Rosenbaum's lack of interest in returning as Lex Luthor. Fans are hopeful, however, that they will finally get to see Tom Welling in his Superman suit.
Birds Of Prey
Set in an alternate future, Birds of Prey saw Gotham City threatened by a new wave of metahuman criminals the police were ill-equipped to handle. Thankfully, the city had a new protector in the form of Helena Kyle (aka The Huntress) - the daughter of Batman and Catwoman, who had developed metahuman powers that gave her enhanced agility, super-strength, a danger-sense, night-vision, and an accelerated healing factor. Helena was joined in her battle by a young telepath named Dinah, her father's butler, Alfred Pennyworth, and her foster mother, Barbara Gordon, who continued to fight crime as the hacker Oracle after being forced to retire as Batgirl.
Ashley Scott's Helena Kyle is joining Crisis on Infinite Earths. Nothing has been said about the rest of the Birds of Prey cast appearing, which is surprising as Dina Meyer's portrayal of Oracle was widely considered to be one of the best aspects of the series. It is unknown if there are any further plans for the character following Crisis, but Helena Kyle would be a natural inclusion to the upcoming Arrow spinoff series focused on the future of Star City and the all-female vigilante team protecting it.