Brendan Gleeson and Colin Farrell star in Martin McDonagh's 'In Bruges,' a Focus Features release.

(L to R) Brendan Gleeson and Colin Farrell star in Martin McDonagh's 'In Bruges,' a Focus Features release.

There is a lot we still don’t know about ‘Joker’ sequel ‘Joker: Folie à Deux’, but the cast is clearly coming together for Todd Phillips’ latest movie.

His most recent addition, at least according to Deadline’s sources, is Brendan Gleeson.

Gleeson joins Joaquin Phoenix, Lady Gaga and Zazie Beetz in the movie, which is looking to incorporate more of a musical element this time around (how that will present in the film is, like everything else, still unknown for now).

Phoenix, of course, is returning as Arthur Fleck, the wannabe comedian-turned-chaos merchant who caused such havoc in Gotham city, spreading murder and mayhem, and who ended up locked away in Arkham Asylum.

Beetz is reprising her role as Sophie Dumond, the single mother and object of Arthur’s affections, even if it turned out to be a fantasy in his head.

As for Gaga, her character has yet to be officially revealed, though there is plenty of chatter at her playing iconic Joker character Harley Quinn, his psychiatrist at Arkham who falls in love with him and becomes his sidekick and partner in crime.

DC Comics' Harley Quinn.

DC Comics' Harley Quinn.

Likewise, Let the speculation commence for how Gleeson might fit into Phillips’ grungy Gotham world. Could he be Commissioner Gordon? Or might he be on the other side of the law, playing a prisoner-patient of Arkham and one of Batman’s rogue’s gallery? Or something new entirely? The possibilities are almost endless…

Co-writer Scott Silver and Phillips have been hard at work on drafts of the script, and the movie’s current working title is ‘Joker: Folie à Deux’ which translates to the term for a mental disorder that affects more than one person. And that’s definitely a good way to describe the viral chaos that Arthur Fleck began scattering around Gotham in the original.

How closely the new movie will hew to established DC lore is unknown at this point – we’d honestly put money on Phillips continuing to chart his own path, picking and choosing how Fleck’s story intersects with the wider Bat-world. And from the sounds of everything we’ve heard so far, this represents the filmmakers branching out from the 1970s crime vibe of the original.

Gleeson is probably still best known for his appearances in several ‘Harry Potter’ movies, though he’s also made a name for himself in the indie world, working on the likes of ‘In Bruges’ and ‘Calvary’.

He’s reunited with ‘Bruges’ director Martin McDonagh and co-star Colin Farrell for their latest, ‘The Banshees of Inisherin’, about lifelong friends who fall out when one of them abruptly ends the friendship.

The film is kicking off its initial festival run with a world Premiere at Venice this week. The movie will then hit theaters on October 21st.

‘Joker: Folie à Deux’ is a little further away, not scheduled for release in theaters until October 4th, 2024.

Joaquin Phoenix in 2019's 'Joker' courtesy of Warner Bros.

Joaquin Phoenix in 2019's 'Joker' courtesy of Warner Bros.