Warning: The following contains SPOILERS for Supergirl season 6, episode 12, "Blind Spots."
John Diggle's latest Arrowverse cameo on Supergirl has only served to muddy the waters regarding his future as a Green Lantern. The long-awaited episode "Blind Spots" found Diggle (David Ramsey) in National City offering a sympathetic ear and helping hand to Kelly Olsen (Azie Tesfai) as she fought against a corrupt city council member and adopted her brother James' super heroic identity of Guardian. Diggle also made perhaps his most direct reference to the Green Lantern Corps to date, but the episode still left it unclear whether or not he had decided to join the intergalactic police force.
Fans of Arrow seized upon the idea of John Diggle becoming a Green Lantern early in the series run, citing both the long partnership between Green Lantern Hal Jordan and Green Arrow in the comics and John Diggle's similarities in background and personality to the Green Lantern John Stewart. The series went on to tease this idea with Diggle briefly meeting The Flash of Earth-90 during the Elseworlds crossover event, where the Barry Allen of another Earth recognized Diggle and asked why he wasn't wearing his ring. Later, the Arrow season 7 episode "Spartan" introduced Diggle's stepfather, United States Marine Corps General Roy Stewart (Ernie Hudson), suggesting that it was entirely possible that John Diggle had taken the surname Stewart in another reality.
The series finale of Arrow teased the idea even further, with one of the final scenes showing Diggle discovering a glowing green object inside a small box that had apparently crashed on Earth like a meteorite. Since that time, David Ramsey has made a number of cameos as John Diggle on other Arrowverse series throughout the 2020-2021 television season. Unfortunately for Green Lantern fans, these appearances have raised more questions than answers regarding Diggle's destiny and his latest appearance on Supergirl may be the most confusing one yet.
John Diggle's Appearance In Batwoman Explained
Diggle's first major Arrowverse appearance after the Arrow finale came in the Batwoman season 2 episode "Rebirth." Diggle happened to be in a private poker club for law enforcement personnel when Luke Fox (Camrus Johnson) confronted the crooked cop that had framed him for attempted murder and stepped in to save Luke after the cop tried to jump him later. Diggle said nothing about his future as a Green Lantern during the Batwoman cameo but did offer Fox some advice on how to cope with the violent death of a father and how to channel your anger over injustice into something positive. As they talked, Fox noted that Diggle seemed pained and Diggle admitted that he had recently been experiencing some fogginess and dizzy spells. This was what had prompted his trip to Gotham City, which had a world-renowned neurology department at Gotham General Hospital.
John Diggle's Appearance In The Flash Explained
Diggle's medical issues were further explored in his next cameo in The Flash season 7 episode "P.O.W." The episode, which found Diggle in Central City working with Team Flash to battle an army of Godspeed clones, dropped several hints regarding the Green Lantern Corps but no direct references. Diggle reported having gotten a clean bill of health from the neurology clinic in Gotham City, but empath Cecile Horton (Danielle Nicolet) claimed that she felt the pain in Diggle's head and sensed that it came from some another presence that felt "huge...no... More like infinite." Later in the episode, Diggle had a dizzy spell during a fight and collapsed to the ground, as a chorus of voices repeated the phrase "worlds await." The episode ended with Diggle leaving Central City before the war with the Godspeed clones was over, telling Barry Allen (Grant Gustin) that there was "something I've been putting off for far too long" that he had to deal with. Footage from the Arrow finale of Diggle discovering the presumed Green Lantern ring was replayed as he said this, once again teasing his future.
John Diggle's Appearance in Superman and Lois Explained
Surprisingly, John Diggle's cameo in the Superman and Lois episode "Through the Valley of Death" offered no new information about just what he had found in the finale of Arrow and if it was connected to the Green Lantern Corps. Diggle appeared in his capacity as an ARGUS agent, personally delivering some advanced technology that General Sam Lane (Dylan Walsh) had requested on behalf of John Henry Irons (Wolé Parks) to build a weapon capable of killing Superman (Tyler Hoechlin). The only reference to what had happened in the Arrow finale during Diggle's Superman and Lois cameo was an angry Diggle telling off General Lane for thinking he'd ever agree to help him kill Superman, complaining that he was trying to get away from his former life as a superhero and be just a regular government agent again. Diggle proclaimed "Dopplegangers, other worlds, glowing boxes, losing the people I love - I'm done with that life." This seemed to suggest that whatever destiny Diggle had been offered by the glowing box had been rejected in favor of a relatively normal life on Earth.
John Diggle's Appearance in Supergirl Explained
The Supergirl season 6 episode "Blind Spots" contained the most direct reference yet to the Arrowverse Green Lantern Corps and just what John Diggle had discovered in the Arrow finale. While talking with Kelly Olsen about her frustrations in fighting systemic corruption as a social worker, Diggle revealed that he recently "had an opportunity to become a special kind of hero" but that it would have required him leaving his family behind. This prompted Diggle to consider that there are many kinds of heroes and what kind of hero he wanted to be. Diggle suggested that Kelly could be a different kind of hero than the Super Friends, focusing her efforts on protecting people from more mundane evils than interdimensional supervillains.
This seemed to suggest that Diggle had rejected the chance to become a Green Lantern in favor of his family. However, this point was later confused near the end of the episode, when Diggle encountered Brainiac-5 (Jesse Rath) on his way out of the Watchtower. The former Legion of Superheroes member seemed surprised and asked if Diggle was returning to Metropolis already. Diggle replied in the affirmative but also said, "Worlds await," as he stepped into the elevator, suggesting that he had decided to accept the new opportunity he had been offered.
Diggle's Choice: Will He Become A Green Lantern?
The context clues in the "Blind Spots" episode of Supergirl seem to have confirmed that John Diggle has been offered a chance to join the Green Lantern Corps. It is also telling that it was the time-traveler Brainiac-5 who witnessed Diggle's departure and seemed to think he might have someplace to go besides Metropolis, since Brainiac-5 would likely know of the Green Lantern Corps' history and the first Earthling to join their ranks. Nothing has been hinted yet as to where John Diggle might appear next in the Arrowverse, but it would be fitting for the first Green Lantern of Earth-Prime to make his debut in the upcoming five-part Flash crossover event Armageddon, which will center around "a powerful alien threat" to the Earth.