One of the biggest collisions of DC heroes almost happened on television — and we don't mean Batman and Superman. In the Arrowverse crossover "Crisis on Infinite Earths," the epic superhero special that aired over episodes of Arrow, The Flash, Supergirl, Legends of Tomorrow, and Batwoman (and some of Black Lightning), the special nearly had the Legends of Tomorrow character John Constantine (played by Matt Ryan) meet the earthy boogeyman Swamp Thing (Derek Mears), from the ill-fated DC Universe series Swamp Thing.
If you know your comics, you know just how intertwined those characters are, and why it's such a bummer that they didn't meet on camera for the first time.
In the March 25 episode of Fake Nerd Podcast, Arrowverse producer Marc Guggenheim joined the show's hosts, where he revealed some new tidbits about the "Crisis on Infinite Earths" special. One of Guggenheim's biggest revelations was his unfulfilled hope to have Constantine meet Swamp Thing in the special.
"I did want Swamp Thing to be a big part of the crossover," Guggenheim said. "If you've got Constantine, to not have Constantine and Swamp Thing together is a missed opportunity."
As to why Constantine didn't meet his old pal from the comics, Guggenheim only said: "I'll just say that, for a variety of different reasons, I couldn't make that happen."
For those unfamiliar with the horror side of the DC Universe, Swamp Thing and Constantine are two DC characters who are as intertwined as Batman and Superman. It was in Alan Moore's legendary 1980s run on the DC Comics series The Saga of the Swamp Thing that introduced John Constantine, a working-class demonologist from London with a nasty smoking habit. In the storyline "American Gothic," Constantine appeared before Swamp Thing, a plant-based elemental creature — formerly a scientist named Alec Holland — to help Swamp Thing get a better hold of his powers.
Constantine's popularity in Swamp Thing encouraged DC to give the character his own ongoing series, titled Hellblazer, which ran for an epic 300 issues from 1988 to 2013. The comic inspired the 2005 Keanu Reeves movie as well as the 2014 NBC series, which lasted for one season before the character joined the Arrowverse franchise in Legends of Tomorrow. In 2019, DC aired a live-action Swamp Thing series on its DC Universe streaming platform before canceling it after just one season.
Onscreen, Constantine and Swamp Thing have never met, which would have made their interaction in "Crisis on Infinite Earths" all the more fulfilling for longtime DC fans. Unfortunately, that simply wasn't in the cards, but at least Constantine still had another unexpected meeting during the special. As for Swamp Thing, he's alone on Earth-12, and it's unlikely he'll return.