NEED TO KNOW
New faces have joined the Wasteland.
In the lead-up to the season 2 premiere on Dec. 16, Prime Video unveiled at least four new Fallout cast members through a mix of official announcements and subtle mic drops. Though not all of their roles are clear, Justin Theroux, Macaulay Culkin, Kumail Nanjiani and Rachel Marsh have signed on for the second season of the apocalyptic drama.
Adapted from the hit video game series of the same name, Fallout is set more than 200 years after a nuclear war devastated the world, forcing survivors into underground Vaults. The series follows Lucy (Ella Purnell), a young Vault dweller who ventures into the dangerous Los Angeles wasteland in search of her kidnapped father, and The Ghoul (Walton Goggins), a legendary ghoul bounty hunter with a complicated past.
As the unlikely duo heads to New Vegas to uncover the truth about Lucy’s dad, they cross paths with some unfamiliar — and potentially dangerous — new players.
Here’s everything to know about the new characters joining season 2 of Fallout.
Justin Theroux as Mr. House
Savion Washington/WireImage; Prime Video
Though Rafi Silver played Robert House (also known as Mr. House) in the first season of Fallout, Theroux is taking over as the mega-rich CEO of RobCo Industries, whom The Ghoul believes caused the end of the world.
The Mulholland Drive star told IGN in December 2025 that his longtime friend Goggins pushed him to take the part, which he was drawn to for the many “delicious scenes” they’d get to do together.
“I guess ostensibly he’s a villain,” the actor said of Mr. House. “But … all villains don’t think they’re villains. They think they’re incredible people that are trying to save humanity and the world, but their wires got crossed somewhere.”
Fallout is just the latest in Theroux’s long résumé of major acting credits from shows like The Leftovers and Running Point to films like The Girl on the Train and Beetlejuice Beetlejuice. He’s been married to Nicole Brydon Bloom since March 2025.
Macaulay Culkin as a member of Caesar’s Legion
Steve Granitz/FilmMagic; Amazon Prime
Deadline reported in November 2024 that Culkin was joining the season 2 cast of Fallout in an undisclosed recurring role. So far, the Home Alone star’s character has only been described as a “crazy genius-type.”
Culkin later revealed to IGN that he plays a member of Caesar’s Legion, a brutal, slave-owning faction in the Fallout universe modeled after the Roman Empire — and that he’s been a fan of this fictional world for some time.
“I’m very familiar with the lore,” the actor told IGN in December 2025, noting that he would even pause the show to explain the “subtle subtext” to his fiancée, actress Brenda Song, when they watched season 1.
Though he hasn’t played the games much, Culkin said he’s dived deep into the “rich world” of Fallout through YouTube videos — and loves that there’s “nothing that is off-brand.”
“You could have zombies in it, you have deathclaws, you have monsters and things like that. I mean, gosh, you have aliens. You name it, you can throw it at the wall,” he said. “There’s no really shape to it. You can kind of stick any kind of shape piece into that hole.”
Best known for his iconic roles as a child star in the Home Alone franchise and My Girl, Caulkin has continued to act as an adult. In addition to voiceover work, he’s appeared in American Horror Story and The Righteous Gemstones.
The actor shares two children with Song, whom he’s been linked to since 2017.
Kumail Nanjiani as a member of the Brotherhood of Steel
Noam Galai/Getty; Prime Video
Fans learned about Nanjiani’s casting in November 2025, after he was featured in the official season 2 trailer. Though the Silicon Valley alum’s exact role hasn’t been revealed, he reportedly plays a member of the Brotherhood of Steel, a secretive organization dedicated to preserving pre-war technology.
Nanjiani revealed during an appearance on Deadline’s Comedy Means Business podcast that he was actually offered the part for season 1, but couldn’t take it due to a scheduling conflict.
“I watched the first season, and I was like ‘Oh man, it would have been nice to be in that,’ ” Nanjiani shared on the podcast in December 2025, adding that he texted Fallout co-creator Graham Wagner after season 1, asking to consider him for a role in future seasons. A few months later, a part became available.
“[Wagner] sent me the script, I read it and I was like ‘This is so fun,’ ” the actor said. “I love the show. I would have done anything on it, but to do like a fun part like that was really, really exciting.”
Off-screen, Nanjiani has been married to Emily V. Gordon since 2007.
Rachel Marsh as Claudia
Gilbert Flores/Variety via Getty
Though Prime Video hasn’t officially announced Marsh’s casting, The Morning Show actress attended the Fallout season 2 premiere in Los Angeles in December 2025.
“I can’t believe I get to be in this show I love,” she captioned an Instagram post from the event.
Not much has been revealed about Marsh’s character, other than that her name is Claudia.
The actress is best known for her roles in Unstable and Adults. In August 2025, Deadline reported that she had been cast in the rom-com adaptation of Ali Hazelwood’s best-selling novel, The Love Hypothesis.
