One of the many great things about Greg Berlanti’s Arrowverse is the number of both prominent and lesser known DC Comics characters that are introduced on each show. And Berlanti definitely made sure to incorporate heaps of Easter Eggs, hints, references and cameos to always keep fans on high alert. However, cameos are usually extremely brief and can sometimes slip through the cracks. With the introduction of the multiverse on The Flash, a bunch of characters from different Earths are showing up quite frequently. On the other hand, the Legends keep on encountering all kinds of alternate pasts, presents, futures and characters. And Arrow has been known to borrow characters, mostly villains, from Batman and Justice League comics.

RELATED: 8 Arrowverse Costumes That Are Better Than The Comics (And 7 That Are Much Worse)

Catching all the references is no easy task, especially in the midst of everything that goes on in an episode. Aside from being very brisk, these references and cameos are at times too obscure to figure out at a moment’s notice without going through the trouble of googling them on the go. So, while we anxiously await our heroes’ imminent return to the small screen, we here at CBR are taking a gander at some of the DC characters you had no idea are already in the Arrowverse.

15 CONNOR HAWKE

Arrowverse Legend's of Tomorrow Connor Hawke

In the comics, Connor Hawke is the son of Oliver Queen and Sandra Moonday Hawke. Connor’s mother told him he was the illegitimate son of Oliver Queen, the hero known as the Green Arrow. Connor trained in martial arts and archery and became the second character to don on the mantle of Green Arrow after the death of his father.

The first time we see an adult Connor in the Arrowverse is in the Legends of Tomorrow episode “Star City 2046,” when the team travels to an alternate 2046 and meets Connor, who took over as Green Arrow following Oliver Queen’s disappearance. However, this Connor Hawke is the son of John Diggle and not Oliver. After Diggle’s death, Connor felt unworthy of his father’s name and changed it. Connor also appeared on Arrow as a John Diggle’s infant son in the main timeline.

14 AQUAMAN

Arrowverse The Flash Aquaman

While the references to the King of Atlantis are rare, we managed to catch a few. Clearly, Aquaman hasn’t made an appearance in the Arrowverse, nor has his name been mentioned in any of the shows. Nonetheless, there have been references to Atlantis.

In fact, several episodes of the second season of The Flash hint at the existence of Aquaman. First, Hunter Zolomon states that he loves Atlantis because one of his best friends lives there. In another episode, Wells opens a world map which shows a large island west of Europe, presumably Atlantis. Finally, in “Escape from Earth-2,” Berry mentions that his parents had always wanted to go to Atlantis. Fun fact, a direct reference to Aquaman did take place in a deleted scene from The Flash’s pilot episode. Trying to convince Berry to stop searching for metahumans, Joe mentions a “man who can talk to fish.”

13 WONDER WOMAN

Arrowverse The Flash Wonder Woman Batman Green Lantern

A huge Easter Egg, only the most meticulous of fans spotted, happened in The Flash’s “Welcome to Earth-2” episode. Barry and Cisco got a glimpse at the alternate universe, as they joined Wells on his trip to Earth-2 to save his daughter Jessie. The episode is filled with cameos, such as a reference to Supergirl, alternate Green Arrow, Connor Hawke and the Justice League of America.

The Justice League of America make an amazing cameo on Earth-2 Barry and Iris’ phone speed dial. Below Bruce and Hal, aka Batman and Green Lantern, appears yet another familiar name - Diana, which is of course Wonder Women’s alter-ego. Although this is only an Easter Egg and none of these characters actually take part in the episode, it is still the first hint at Wonder Woman in the Arrowverse.

12 BRAINIAC

One of the most prominent villains from Superman’s rogues gallery, Brainiac, is a techno-organic AI who kidnapped the entire Kryptonian city of Kandor by miniaturizing it. Brainiac's extremely advanced mental abilities enable him to work through a number of robotic and human proxies. One of his many descendants, Brainiac 8, aka Indigo, was designed in a distant future to advance Brainiac’s plans by infiltrating enemy troops.

The highly intelligent synthetic being Indigo made an appearance on Supergirl as the Fort Rozz’s most dangerous prisoner with plans to destroy humanity. Needless to say, Indigo’s role on Supergirl didn’t have much in common with her role in the comics. And even though, Brainiac himself hasn’t yet shown his face in the Arrowverse, his existence can certainly be inferred from the existence of Indigo.

11 BATMAN

Arrowverse The Flash Batman

Given Arrow’s uncanny resemblance to the Dark Knight and all the Batman villains that have appeared on the show, many were wondering if Batman even exists in the Arrowverse. While the Caped Crusader hasn’t made an official appearance yet, there have been several references indicating that he is indeed part of the Arrowverse.

The existence of Harley Quinn and Oracle somewhat indicate the presence of Batman in Gotham, but there have also been direct references to Bruce Wayne and his alter-ego. In the first episode of The Flash one of the titles in a future newspaper reads “Wayne Tech/Queen Inc Merger Complete.” In Legends of Tomorrow, Rip Hunter references to two members of the Trinity, when he says “I’ve seen men of steel die and dark knights fall,” proving once and for all that Batman is already in the Arrowverse.

10 ORACLE

15 Times Super Women Fought Back

In the comics, the character who goes by the codename Oracle is none other than Barbara Gordon. During the “The Killing Joke” storyline, Barbara was shot and paralyzed by The Joker. Realizing her career as Batgirl was over, Barbara assumed the identity of Oracle and developed a highly complex and powerful computer system which accumulated information on just about anything, proving herself as an invaluable resource to Batman.

When Felicity was shot and paralyzed by Oliver’s enemies during season four, many were quick to draw parallels. Seeing as Felicity has been doing the same for Team Arrow as Oracle was for Batman, the fans theorized that Felicity would be taking on the codename Oracle. However, this was promptly rebutted when Oliver dubbed Felicity as Overwatch, stating that he wanted to go with Oracle, but it was already taken. Hinting that Oracle, aka Barbara Gordon, does exist in the Arrowverse.

9 GREEN LANTERN

Arrowverse Arrow Green Lantern Hal Jordan

Greg Berlanti sure loves dropping names. Apart from Ferris Air and Coast City references indicating that Hal Jordan, aka Green Lantern, is part of the Arrowverse, there is even more conclusive evidence in support of this theory.

In The Flash episode “Rogue Air,” Barry makes a reference to Hal Jordan when he explains that the Farris Air Testing Facility has been shut down because a test pilot went missing. In a flashback during Arrow’s first episode of season four, Oliver is shown talking to Amanda Waller at a bar in Coast City and a man in a green jacket walks past them. The most vigilant fans caught the man’s name tag, which reads “Jordan.” So, now that we know for certain Hal Jordan exists in the Arrowverse we’re anxiously awaiting his big entrance.

8 KOMODO

Arrowverse Komodo Arrow

Simon Lacroix, aka Komodo, is one of the many archer enemies of the Green Arrow. In the comics, the highly intelligent and sly Simon gets a position at Queen Industries and becomes a protege of Robert Queen. At the time Oliver was still an irresponsible playboy and Robert saw in Simon everything Oliver was lacking. However, Simon later betrayed and murdered his mentor. Assuming his alter-ego Komodo, Simon framed Oliver for Robert’s death.

Komodo appeared briefly on Arrow during season three as a mercenary suspected of killing Sara Lance. Team Arrow managed to hunt him down, but Komodo denied killing Sara and fled the city. While, Komodo did look rather similar to his comic book counterpart, he barely got any development and not much came of his appearance on the show. Hopefully, the good folks at The CW will give Komodo a second chance.

7 FIREFLY

Arrowverse Arrow Firefly Garfield Lynns

Originally a pyrotechnic expert for motion pictures, Garfield Lynns fell victim to Gotham’s poverty and turned to the life of crime. To satisfy his pyromaniacal tendencies he created a jetpack and a flamethrower, becoming the serial arsonist known as Firefly, one of Batman’s major nemesis.

In its first season Arrow relied heavily on borrowing plotlines and villains from Batman comics, as was the case with Firefly. However, Firefly was very poorly adapted in the Arrowverse. Instead of a deluded pyromaniac with a flamethrower, we got a guy with a flair for setting stuff on fire and a revenge against his former fellow firefighters. Obviously, Arrow’s Firefly did not share a whole lot with his comic book counterpart. Sadly, Firefly took his own life by setting himself on fire, so the writers don’t get a second chance with him.

6 HARLEY QUINN

Arrowverse Arrow Harley Quinn

Joker’s sweetheart and the original overly attached girlfriend, Harley Quinn is one of those characters who needs no introduction. Former Arkham Asylum psychiatrist, Harleen Quinzel assumed her alter-ego after falling madly in love with The Joker. Over the years, she became a fan favorite, so everyone was pretty hyped when Arrow dropped the biggest tease in the history of Arrowverse.

Back in 2014, before the disaster known as the Suicide Squad movie, Arrow introduced its own version of the Suicide Squad. While Diggle and Lyla were busy arguing about A.R.G.U.S. letting dangerous prisoners roam around acting as disposable human weapons, we got a sneak peek at one of the most notorious members of Task Force X, Harley Quinn. Granted, we only saw the back of her head and not her face, but we did hear her say she was a trained psychiatrist.

5 CAROL FERRIS

Arrowverse The Flash Carol Ferris

In the comics, Carol Ferris is the president of Ferris Air, a company based in Coast City. After her father retired, Carol was left in charge of the family business. Carol hired Hal Jordan as a test pilot and soon fell in love both him and Green Lantern, not knowing they were the same person. She later became a hero, occasionally a villain, named Star Sapphire.

So far, Carol hasn’t made an appearance in the Arrowverse. However, there have been numerous references to her and her company. Ferris Air billboards can be seen in many Arrow and The Flash episodes. Plus, the closed Ferris Air Testing Facility has been used several times on The Flash. On one occasion, Barry even made a comment that the facility got shut down after one of their test pilots disappeared. Wink wink nudge nudge.

4 BLUE BEETLE (TED KORD)

Arrowverse The Flash Blue Beetle Ted Kord

In the comics, Ted Kord is the second character to take on the mantle of Blue Beetle, upon the request of his archeology teacher and the first Blue Beetle, Dan Garrett. After his mother’s death and his father’s subsequent depression, Ted took over Kord Industries and rebuilt the company.

In Arrow’s first season episode “Undertaking,” Robert and Moira Queen attend a fundraiser held by Ted Kord. Throughout both The Flash and Arrow, there have been countless references to Kord Industries. At one point, Felicity even worked there. In fact, Blue Beetle was supposed to appear on Arrow, played by Brandon Routh. However, Warner Bros. announced a Blue Beetle and Booster Gold movie and Routh got to play the Atom instead. Still, considering the overwhelming evidence, it’s a safe bet that Blue Beetle does exist in the Arrowverse.

3 ACCELERATED MAN

Arrowverse The Flash Accelerated Man

Blink and you’ll miss it. The Earth-19 equivalent of The Flash, known as Accelerated Man, appeared briefly in The Flash’s season three episode “Attack on Central City.” We caught a brief glimpse of the speedster when Gypsy went back to Earth-19 to pass him some information and photos. Seconds later Accelerated Man perished, leaving a trail of purple lightning in his wake.

Unlike most names on the list, Accelerated Man is not a huge DC character and unless you’re well versed in comics you probably missed this reference. Not much is known about Accelerated Man, except that he’s Earth-19’s version of The Flash and he’s a member of the Collectors. What most fans are wondering is why is his lightning purple and when do we get to see him again.

2 DOCTOR FATE

Arrowverse Constantine Doctor Fate

Doctor Fate is one of the most powerful and oldest heroes in DC Comics. Over the years, different characters have assumed the identity of Doctor Fate. However, the most popular is Kent Nelson. Kent got his powers from Nabu, a powerful sorcerer and magician residing within the Helmet of Fate. The Helmet of Fate together with the Amulet of Anubis and the Cloak of Destiny make up Doctor Fate.

The Helmet of Fate appeared in the series premiere of NBC’s Constantine. Even though Doctor Fate did not appear on the show, the helmet we saw was unmistakably The Helmet of Fate. Unfortunately, Constantine was cancelled after only 13 episodes, leaving many questions unanswered. The good news is, The CW brought John Constantine into the Arrowverse in Arrow’s fourth season episode “Haunted,” which means that everything that happened on Constantine is canon, including Doctor Fate’s existence.

1 THE JOKER

Arrowverse Arrow The Joker

DC Comics’ biggest supervillain, Batman’s archnemesis and a deranged serial killer, The Joker is one of those characters you absolutely have to appreciate. This brilliant and deadly criminal mastermind needs no motivation to kill other than to satisfy his own sadistic needs. Certainly, if he had appeared in the Arrowverse he would not have gone unnoticed.

Still, even if Joker hasn’t exactly popped up yet, there are indications that he is spending his days traumatizing the citizens of Gotham. With strong allusions to both Harley Quinn and Oracle, it can be concluded that Joker too exists in the Arrowverse. He is after all the one responsible for turning Harleen Quinzel and Barbara Gordon into their alter-egos. Granted, chances are we won’t actually get to see Joker, unless Berlanti decides to make a Batman spin-off.

So, which one of these hidden characters surprised you the most? Let us know in the comments!