Black Lightning will join the Arrowverse in the Crisis on Infinite Earths crossover, but how the DC Comics superhero will be implemented in the event remains a mystery. However, the crossover's focus on alternate realities is likely the key, since Black Lightning has always been separate from the Arrowverse.
This year's annual Arrowverse crossover is expected to be the biggest one yet. The five-part event will encompass Arrow, The Flash, Legends of Tomorrow, Supergirl, and the newest Arrowverse series, Batwoman. The story will be tied to the end of Oliver Queen's story in the final season of Arrow, as well as the entire plot of The Flash's sixth season. With guest stars like Burt Ward (who played Robin in the 1960s Batman series) and longtime Batman voice actor Kevin Conroy as an older version of Bruce Wayne, it's easy to see why Crisis on Infinite Earths is so important to the Arrowverse.
In early August, Black Lightning star Cress Williams confirmed his involvement in Crisis on Infinite Earths, which was surprising since it's been stated on multiple occasions that Black Lightning does not take place in the Arrowverse. That would normally mean that any crossover between it and any of the other shows would be difficult to work out. However, Crisis on Infinite Earths deals extensively with alternate realities, which means that Black Lightning can join the Arrowverse similar to the way that Barry Allen first encountered Supergirl.
Black Lightning wouldn't be the only character from a parallel Earth to appear in the event either. Legends of Tomorrow's Atom actor, Brandon Routh, who portrayed the Man of Steel in Superman Returns, will play the Kingdom Come version of Superman in Crisis on Infinite Earths. The Kingdom Come Superman and Black Lightning could be just two of many alternate reality heroes to take part in the crossover. If all of reality is at stake, heroes across every Earth could be called in to help.
If Crisis on Infinite Earths is like its namesake and involves multiple realities being eliminated and merged into one, this could be a potential problem for the world of Black Lightning. But since showrunner Salim Akil has been adamant about Black Lightning existing in its own universe, it's unlikely that anything that happens in Crisis on Infinite Earths will have any sort of meaningful effect on The CW series.
Interestingly, Williams has yet to elaborate on which of the five episodes his character will make an appearance. Since the crossover is already packed with major characters and guest stars, it's possible that Black Lightning's role will be limited to only one or two episodes. Also, it's not clear if the other superheroes in Black Lightning will join Jefferson Pierce in the action, but regardless of that, just having another TV series based on DC Comics in the event is just one more reason to be excited about Crisis on Infinite Earths.