Interesting details about the Joker sequel, Joker: Folie à Deux, are slowly being dribbled out, such as it being a musical and Lady Gaga playing Harley Quinn, and it has just been revealed that Gleeson has been cast in an unknown role. The Golden Globe-nominated actor's typically gruff roles fit perfectly with the filthy and crime-riddled 80s Gotham in Joker, but there's a huge number of possible characters he could be playing.

The 2019 movie didn't tease many other characters in the world, but based on everything fans know about the upcoming sequel, it's easy to deduce the role down to a handful of characters. Between well-known Batman villains, characters from games that only die-hard fans know, and a completely original character, Gleeson could play any one of them.

Dr. Hugo Strange

Hugo Strange from a DC comic.

Dr. Hugo Strange hasn't had a presence in any of the live-action Batman movies, which comes as a surprise, considering he's such a major villain. Batman's villain is a psychiatrist at Arkham Asylum, and as Joker 2 will have an Arkham setting, Hugo Strange will likely appear in some capacity.

As the first movie took inspiration from classic 70s movies like Taxi Driver, Joker 2 could do the same by taking influence from One Flew Over the Cuckoo's Nest, as Strange could be Arthur Fleck's very own Nurse Ratched. Gleeson would be the perfect choice for Strange, as his best performances see him playing intimidating characters, most notably in the crime drama series Mr. Mercedes.

Harvey Bullock

Harvey Bullock in Batman the Animated Series

Based on Gleeson's character in In Bruges, which is about two lovable hitmen on the run and hiding in the titular European city, he would nail Harvey Bullock, a detective in the Gotham world who isn't dirty, but it isn't exactly clean either. However, if Joker 2 is set not long after the first movie and still has a 80s setting, it might be a little too early for Bullock to appear, as he was never that old.

The character was seemingly not much older than Bruce Wayne, only he didn't take care of himself half as well. But it's hardly as if Joker followed the source material or timelines that closely, and it's easy to see Gleeson as Bullock in that setting. What would have been better is if one of the detectives who interrogated Arthur in the first movie was Bullock, as that would have been the perfect setup for a bigger role in the sequel.

Quincy Sharp

Quincy Sharp in Batman Arkham Asylum

Quincy Sharp is the warden of Arkham Asylum in the highly influential video game of the same name. Given that the hospital will have a major role in the movie, it's likely that Sharp may appear in Joker 2. If this is the case, it'd mark the first time a Batman-related movie has used characters from the video game series.

The character would fit into the world of Joker much better than Hugo Strange, as he's much less theatrical and fantastical, and he's more of a quietly evil and vindictive antagonist. Though Gleeson doesn't match Quincy's physical profile, the actor could easily pull off a trustworthy doctor who's secretly a serial killer. It'd be as if his two typical roles collided, as he's always cast as either a well-mannered and wise character or a criminal.

Commissioner Gordon

J.K. Simmons cast as Commissioner Gordon in Justice League Part 1

One of the likeliest and more logical characters that Gleeson could be playing is Commissioner Gordon, who has always been an imperative character in the Batman franchise. Given that Joker 2 will most likely see Arthur Fleck grow into the criminal mastermind the Joker is known as, there has to be an authoritative figure of some sort for there to be any kind of stakes and consequences, and Gordon makes the most sense.

At this early point in his career, Gordon would be the scrappy and not at all by-the-book cop that he became later in his career, as he even left a criminal naked in the snow in Batman: Year One. Though Gleeson might seem too old to play Gordon's scrappy 80s version, he could still be a more rough-around-the-edges version of the character than the archetype that audiences are used to seeing.

The Penguin

Colin Farrell as the Penguin seated at a table in The Batman.

It'd be a bold move to include the Penguin in the sequel, as the iconic villain had a prominent role in the recently released The Batman, will have his own HBO Max show, and will most likely have an even bigger role in The Batman 2. If Penguin was in Joker 2, it might confuse a few casual viewers.

However, there are so many different incarnations of the Joker in current movie series, so audience's confusion barely seems like something Warner Bros. is worried about. Out of all the possible Joker 2 villains, the Penguin doesn't seem very likely, but Gleeson would make a great Oswald Cobblepot. His role as Alastar Moody in the Harry Potter franchise showcased how great the actor was at playing mysterious and creepy characters.

Chief O'Hara

Chief O'Hara in the 1960s Batman television series

The Batman had so many references to the 1960s series, so it isn't as if the campy show is completely forgotten. The 2022 movie even featured Aunt Harriet, a character who was only ever seen in the 60s show, and Joker 2 could continue that trend of extremely dark Batman movies paying homage to the 60s Batman.

Chief O'Hara was only ever featured in the 60s series, and he was a Gotham police officer who sometimes let his emotions get the best of him. Gleeson could have fun with the role, as he could only be a comic relief character, and given how the character is Irish, it'd be totally on-brand.

Ratcatcher

The Subtle Nod To Batman Villain Ratcatcher

Once again, Ratcatcher already exists in a separate DC movie universe, as his daughter's version was one of the best characters in The Suicide Squad, but that doesn't mean a different iteration of him can't appear in Joker 2. Though Ratcatcher sounds a little too outlandish for the Joker world, as the supervillain has the ability to communicate with rats, Joker already hinted at the possibility of the character appearing.

In the 2019 movie, the Gotham Department of Sanitation is on strike, as garbage collectors had refused to work for a whole 17 weeks. And as a result, cat-sized rats were roaming the city. That's the perfect introd for Ratcatcher, and the grubby villain is a typical role for Gleeson, who has rarely turned down the opportunity to play a dirty and seedy character.

Harvey Dent

Aaron Eckhart as Harvey Dent in The Dark Knight

Though the twin bouncers did set up Batman's best movie villain Two-Face in The Batman, as they're henchmen for Harvey Dent in the comic books, there's little else in the 2022 movie that points toward the district attorney being in the sequel. The start of the trilogy was way more preoccupied with setting up other villains, and Joker 2 could take full advantage of that.

Harvey Dent could fit perfectly in the Joker universe, as Gotham City has never needed cleaning up more than the one found in the 2019 release. Gleeson would be unlike any Harvey Dent fans have seen on the big screen, and it'd be another role that could perfectly showcase both the sweet side and the darker side of the actor.

Solomon Grundy

Solomon Grundy in the comics

Solomon Grundy is a popular character in the DC universe at large, as he's one of Superman and even Swamp Thing's enemies. But above all else, he's one of Batman's biggest villains. And in Emperor Joker, which sees the Clown Prince of Crime warping reality, he's even the warden of Arkham Asylum.

As Joker 2 is confirmed to be something of a musical, which will most likely take place in Arthur's mind, it'd be easy to have Solomon Grundy as the warden in one of the failed stand-up comedian's hallucinations. Gleeson has always embraced the theatrical side of movies and has never been shy when it comes to dressing up and being put in less than flattering make-up. In that respect, Grundy could be one of Gleeson's more entertaining performances.

A Brand New Character

Brendan Gleeson as Professor Moody in Harry Potter

Very few Batman movies have ever featured original characters, and even the tertiary characters are borrowed from the comic books or the animated series. However, most of the characters in Joker were created for the R-rated movie, including one of the main characters, Murray Franklin (Robert De Niro).

Murray played a major role in Arthur Fleck's transition into the Joker, and there's a good chance that Gleeson could be playing an original character in Joker 2, just like De Niro did in the first film. And regardless of whether it's an Arkham Asylum orderly, a dirty cop, or anyone else, Gleeson has enough range that he could nail any one of them.

NEXT: 10 Classic Songs That Should Be Covered In The Musical Sequel Joker 2