WARNING: The following article contains major spoilers for “The Trial of The Flash,” the midseason premiere of The Flash.
Fans have been teased for years with hints that Hal Jordan could eventually join The CW’s Arrowverse. From Ferris Air ads to references to a missing test pilot to a fleeting cameo by a man wearing a bomber jacket emblazoned with the name “Jordan,” Arrow and The Flash have made a conscious effort to keep the cocky space cop’s potential arrival a lingering, if relatively minor plot thread. However, The Flash's midseason premiere may very well have set up the perfect entry point for not just Hal Jordan but the entire Green Lantern Corps.
In last week's “The Trial of The Flash,” which takes its title from the classic DC Comics storyline, Grant Gustin's Barry Allen is forced to skip out on his own trial to help stop a radiation-emitting metahuman dubbed Fallout by Cisco. After using his super-speed to create a vacuum to contain Fallout’s radiation, Barry realizes he’s unable to hold it for long. Wells, due to his vast knowledge of the Multiverse, recommends they send Fallout’s – well, fallout – to Earth-15, which he describes as a “dead Earth.” Without skipping a beat, Cisco vibes open a portal and Barry once again saves the day (only to later be found guilty of of the murder of Clifford DeVoe).
On the surface, that reference to Earth-15 might not seem like much, but looking to the comics, the parallel world holds a significant place in Green Lantern lore.
When the DC Multiverse was reshaped following the events of 2011's Flashpoint, Earth-15 – once home to heroes who had evolved into nigh-perfect beings – was replaced by Earth 15 (no hyphen). In this version, the once-picturesque planet is now a barren wasteland, and all that remains is the mysterious Cosmic Grail, a pseudo-Green Lantern power battery, which is lost somewhere in the depths of the Multiverse.
Before it was a graveyard, however, Earth 15 was home to the Green Lantern villain known as Volthoom, the First Lantern. In the year 3079, upon learning that his world was destined to be destroyed, Volthoom created the Travel Lantern, allowing him to journey through the Multiverse to find a way to save his planet. Eventually, he arrived on Earth 0, 10 billion years in the past, in the lab of Krona. Not only was this right around the time that the Maltusians conducted an experiment to witness the beginning of all existence, effectively creating the Multiverse and the Antimatter Universe, but it was also here that the first Power Ring was created, granting Volthoom a divine connection to the Emotional Spectrum.
However, in the recent Green Lanterns run written by Sam Humphries, it was revealed that Volthoom was ultimately responsible for the destruction of his homeworld. To prevent him from returning to his timeline and bringing about the end of the planet, the Guardian of the Universe known as Rami destroyed the Travel Lantern, and in doing so, created the first Green Lantern rings.
Obviously, Wells’ reference to Earth 15 could've been nothing more than a throwaway line -- an Easter egg for DC Comics devotees -- and it’s hardly the first time other Earths have been called out by name on The Flash. On the other hand, if the Green Lantern Corps were to enter the Arrowverse, dedicating an entire universe to them would certainly be an interesting way to introduce DC's space cops without burdening them with the day-to-day superheroics on Earth-1.
Airing Tuesdays at 8 pm ET/PT on The CW, The Flash stars Grant Gustin as Barry Allen, Carlos Valdes as Cisco Ramon, Danielle Panabaker as Caitlin Snow, Candice Patton as Iris West, Jesse L. Martin as Joe West, with guest appearances from Keiynan Lonsdale as Wally West and Hartley Sawyer as the Elongated Man.