Legends of Tomorrow Season 4 will be ripe with monsters both magical and maniacal as the team works to seek and destroy the evil that scattered throughout the land after Mallus' defeat. This magical season could even set the stage for a cameo or future crossover, as Matt Ryan's Constantine name-checked a character starring in an upcoming DC Universe series. Does his Swamp Thing reference possibly mean there's a connection between the two shows? Take a look at the trailer for yourself, below:
The line feels significant, especially since it stands out in a trailer that features a homicidal unicorn and what appears to be a fairy godmother yelling "bitch." Would Legends of Tomorrow include a nod to Swamp Thing in its trailer if it only planned to turn around and disappoint those hoping for a crossover? Granted, the line feels almost mandatory given the Legends will take on some "swampy monster thing" in Season 4, but still feels as though it, at the very least, opened up the door for a future collaboration between Legends of Tomorrow and Swamp Thing.
Constantine and Swamp Thing have a pretty solid history in DC lore, so it would make sense if Swamp Thing wanted to bring actor Matt Ryan into its show to play Constantine at some point. In the comics, Constantine helped Swamp Thing increase his powers, introduced him to the Green and Parliament of Trees, and even allowed him to use his body so Swamp Thing could make love to his wife. That's a bond not many men share, so it would definitely be cool to see the two cross paths in some way in the future.
As cool as that may be, there are reasons to doubt that Constantine's line in the Legends of Tomorrow trailer meant a crossover is happening. Gary Dauberman, who wrote the Swamp Thing pilot and is serving as executive producer, said earlier this year that a Titans crossover with his show had not been discussed, and that the dramas will not connect right away. One would imagine if an intra-DC Universe crossover was not discussed, a DC Universe and Arrow-verse crossover wasn't either. This information makes Constantine's line feel less substantial, and more akin to Cisco Ramon's Marvel references on The Flash, than an actual clue the shows will collide any time soon.
We also know from Swamp Thing's show description that Abby Arcane and Alec Holland share a brief relationship before his tragic death and transformation. Given that information, and the fact that Swamp Thing doesn't premiere until 2019, it may not make chronological sense that Constantine would know Swamp Thing when he says he does. This could be explained away by Legends of Tomorrow's frequent time-travel, if a deal was worked out, but right now it could mean that Constantine is talking about a different Earth's Swamp Thing.
A Legends of Tomorrow and Swamp Thing crossover could be a big deal, as it has the potential to be the first major bridge connecting DC Universe and the Arrow-verse. Legends of Tomorrow might be the perfect program to start that relationship, as its zany nature and somewhat irreverent humor may work better with the darker toned DC Universe shows than lighter, more mainstream superhero affairs like The Flash. We'd for sure love to see the DC Universe hero lineup present at a potential "Crisis on Infinite Earths" mega-miniseries, although that all feels like a distant dream at the moment.