James Gunn's Superman quietly revealed some of the new DCU's 300 year legacy of superheroes

James Gunn's Superman exists in a world full of superheroes, which includes the Justice Gang that hangs out in its under-construction headquarters, the Hall of Justice – one of the classic home bases of the comic book Justice League. But the Justice Gang heroes aren't the only ones in the hall, as there's a whole mural on the wall depicting superheroes going back 300 years (or potentially more), as established in the intro of the film – and it includes the world's first ever superhero team, the Justice Society of America.

The JSA is the real world's first superhero team. First appearing all the way back in 1940's All-Star Comics #3, the JSA was the first group of heroes assembled from across other comic books. A version of the team based on the JSA's modern incarnation appeared in the ill-fated Black Adam movie, and the characters of Kendra Saunders/Hawkgirl and Michael Holt/Mister Terrific of the Justice Gang also came to prominence in the late '90s version of the JSA.

In terms of who's on the mural, which can be glimpsed in some of the film's trailers – the JSA members seen include the Spectre, Wildcat, Sandman (the '40s mystery man, not the mythical demigod), and of course, Jay Garrick, the original Flash.

This seems to indicate that the JSA also existed in the history of the new DCU, in an era visited by Creature Commandos in its flashbacks to GI Robot's WWII past.

Other characters seen on the mural include the medieval hero Silent Knight, the 16th century vigilante the Black Pirate, the sci-fi armored hero Atomic Knight, Indigenous hero Black Bison, and Vibe of the Justice League, known for his role in CW's Flash show. Perhaps most interestingly, the mural also includes the otherworldly fantasy hero Amethyst, Princess of Gemworld, who was hinted at in Creature Commandos.

Gunn confirmed the intent of the mural in an interview with Buzzfeed.

"It's a giant Easter egg. The scene where the Justice Gang is in the Hall of Justice," Gunn says, explaining that the real location where they filmed the scene has a real life historical mural. "We replaced that with a mural of the metahumans that have existed in the DCU over the years."

We'll have to wait and see just how these heroes of the past will fit in as the DCU continues to grow, but for now, the mural is another hint at the history of the new DC Universe and how it might continue to show the heroes that have come before.

Superman is in theaters now. For more, check out our guides to all the upcoming DC movies and TV shows and how to watch the DC movies in order.