The Marvel Cinematic Universe (MCU) is no stranger to spectacle, but Avengers: Doomsday, set to hit theaters on December 18, 2026, is shaping up to be its most audacious gamble yet. Helmed by the Russo Brothers and featuring Robert Downey Jr. as the formidable Doctor Doom, this fifth Avengers installment promises a multiversal clash of epic proportions, uniting the Avengers, Fantastic Four, X-Men, and Thunderbolts against a villain who could outshine Thanos. But behind the scenes, whispers of chaos are swirling: the film is deep into production without a finalized script, with action sequences being filmed on the fly and the cast—some still unsigned—navigating a narrative that’s evolving daily. Is Marvel’s high-stakes, freewheeling approach a recipe for brilliance or a blockbuster disaster? Buckle up as we dive into the wild, unpredictable world of Avengers: Doomsday and why its chaotic production could redefine the MCU—or break it.
A Multiversal Puzzle Without a Blueprint
Avengers: Doomsday is not just another superhero flick—it’s the penultimate chapter of the MCU’s Phase Six and the Multiverse Saga, a sprawling narrative that began with Avengers: Endgame’s time-bending triumph in 2019. The film, originally titled The Kang Dynasty, was reimagined after Jonathan Majors’ legal issues prompted Marvel to pivot from Kang the Conqueror to Doctor Doom, played by Downey in a shocking return after his iconic run as Tony Stark. Directed by Anthony and Joe Russo, with a screenplay by Michael Waldron and Stephen McFeely, Doomsday boasts a jaw-dropping cast: Chris Hemsworth as Thor, Anthony Mackie as Captain America, Vanessa Kirby as Sue Storm, Pedro Pascal as Reed Richards, and X-Men veterans like Patrick Stewart (Professor X), Ian McKellen (Magneto), and Rebecca Romijn (Mystique). But the real twist? Principal photography began in April 2025 at Pinewood Studios in England, and three months later, the script remains unfinished, with scenes being rewritten on set and actors unsure of their full roles.
This isn’t Marvel’s first rodeo with a fluid script. Iron Man (2008) was famously improvised during the 2007 writers’ strike, with Downey and Jeff Bridges ad-libbing key scenes to create a classic. Avengers: Infinity War and Endgame were filmed with evolving scripts, yet the Russo Brothers delivered a cohesive two-part epic. But Doomsday’s scale is unprecedented, juggling Avengers, Wakandans, the Fantastic Four, Thunderbolts, and Fox-era X-Men in a multiversal showdown. Sources report that Marvel is filming massive action sequences—like a rumored Fantastic Four vs. X-Men battle—without a locked narrative, filling in character arcs and dialogue later. Rebecca Romijn, reprising her role as Mystique, admitted at San Diego Comic-Con 2025, “I’m not quite sure [if I’m done filming]. The script hasn’t—they haven’t finished writing it.” Her candid remark, echoed by Alan Cumming (Nightcrawler), who said he didn’t always know who he was acting with, paints a picture of a production that’s thrillingly chaotic but teetering on the edge.
The Russo Brothers’ High-Wire Act
The Russo Brothers, who helmed Captain America: Civil War, Infinity War, and Endgame, are no strangers to juggling complex narratives. Their return, alongside Downey as Doctor Doom, was announced at San Diego Comic-Con 2024 to thunderous applause, seen as a bid to recapture the MCU’s Infinity Saga glory after a rocky Multiverse Saga. But their recent projects, like The Gray Man and Citadel, haven’t matched their Avengers-era success, raising eyebrows about their ability to tame Doomsday’s chaos. Kevin Feige, Marvel Studios president, defends the approach, calling it “plus-ing”—a collaborative process where actors, writers, and directors refine the story on set. “There’s plus-ing happening every day on the Avengers: Doomsday set right now, and it’s amazing to watch,” Feige said, emphasizing the input from veterans like Downey and newcomers like Pedro Pascal.
This method has upsides: Simu Liu (Shang-Chi) described filming as “a dream,” working alongside icons he admired as a kid. Channing Tatum, playing Gambit, teased a “big fight” with Downey’s Doom, hinting at action sequences that are already electrifying the set. But the risks are glaring. Without a finalized script, narrative cohesion could suffer, with pacing issues or underdeveloped arcs threatening the film’s $300 million budget. Social media is abuzz with concern, with one X user warning, “The amount of rewrites while actively filming and fights on set are never a good sign.” Another called it “corporate movie-making-by-committee,” fearing a lack of heart in favor of CGI spectacle. Yet, optimists point to the Russos’ track record, noting that Endgame’s script evolved during production and still delivered a cultural juggernaut.
A Cast of Legends, A Script in Flux
The Doomsday cast is a Marvel fan’s dream, blending MCU stalwarts with Fox’s X-Men and the debut of the Fantastic Four from The Fantastic Four: First Steps (2025). Anthony Mackie’s Sam Wilson, now Captain America, leads a new Avengers lineup post-Captain America: Brave New World. Letitia Wright’s Shuri, Florence Pugh’s Yelena Belova (Thunderbolts), and Tom Hiddleston’s Loki join the fray, alongside X-Men like James Marsden (Cyclops) and Kelsey Grammer (Beast). Chris Evans returns, possibly as Steve Rogers or a variant, with rumors of a scene featuring him, Hayley Atwell’s Peggy Carter, and Downey’s Doom set in the past, filmed at Windsor Great Park. Ryan Reynolds’ Deadpool and Paul Rudd’s Ant-Man add levity, with Rudd crashing a Russo Brothers’ video update at D23 2025, blocking the camera in classic Ant-Man style.
But the unfinished script means some actors are filming without knowing their full arcs. Romijn’s uncertainty about her scenes and Cumming’s comment about not knowing his co-stars highlight Marvel’s secrecy and the production’s fluidity. Sources suggest Marvel is still locking in deals with some actors, complicating the script’s development. John Rocha, a scooper, noted that the cast’s uncertainty “could lead to a chaotic filming schedule,” with the Russos directing scenes based on “beats” rather than a complete story. Yet, this approach allows flexibility—actors like Downey, who’s played Tony Stark for a decade, bring deep character knowledge, suggesting dialogue tweaks or improvisations that could elevate the film. The challenge is weaving these performances into a coherent narrative, especially with a multiversal plot involving the TVA (Time Variance Authority) and a rumored “Final Incursion” that could set up Avengers: Secret Wars (2027).
Action First, Story Later
Marvel’s strategy for Doomsday prioritizes spectacle, filming tentpole action sequences at Pinewood Studios, Windsor Great Park, and Bahrain, then building the story around them. Reports confirm a Fantastic Four vs. X-Men sequence and a major TVA scene, with Tom Holland’s Spider-Man spotted alongside Simu Liu, suggesting a multiversal crossover. These sequences, requiring months of VFX work, are being shot early to meet the December 2026 deadline, with editors like Jeffrey Ford tasked with stitching them together. Alan Silvestri, returning to score Doomsday and Secret Wars, is crafting a musical backdrop that could rival his Infinity War themes, but the lack of a locked script means he’s composing to an evolving vision.
This “action-first” approach has precedent. Infinity War and Endgame filmed key battles before finalizing scripts, relying on the Russos’ ability to balance scale with character moments. But Doomsday’s massive cast—potentially triple the speaking roles of Infinity War—and the integration of X-Men and Fantastic Four make it a logistical nightmare. Social media reflects the divide: one Reddit user argued, “Rewrites during filming are normal… The Russos know what they’re doing,” while another warned, “This is a $300M movie meant to be pivotal. No script, no vision, just CGI set-pieces stitched together.” The Fantastic Four’s lukewarm box office and Thunderbolts’ mixed buzz add pressure to deliver a hit that restores MCU faith post-Ant-Man: Quantumania.
A Cliffhanger to Shake the Multiverse
Anthony Mackie teased a “cliffhanger ending” that “pushes the boundaries,” hinting that “everyone is expendable.” This ominous warning suggests Doomsday could echo Infinity War’s gut-punch finale, with permanent deaths or a multiversal collapse leading into Secret Wars. The pivot to Doctor Doom, whom Feige called the only villain to match Thanos’ grandeur, was planned before Ant-Man: Quantumania’s 2023 release, but its last-minute nature has fueled the script’s delays. Downey’s Doom, a Latverian genius with mystical and technological prowess, is a bold choice, but fans are divided—some thrilled by his return, others skeptical after Tony Stark’s perfect Endgame exit.
The production’s chaos could be its strength or its Achilles’ heel. Marvel’s “plus-ing” philosophy allows for creative breakthroughs, but risks narrative incoherence. The Russos’ vision of Doomsday as a “new beginning” for the MCU, contrasting Endgame’s closure, hinges on balancing spectacle with heart. Locations like Bahrain’s deserts and Windsor’s historic park promise visual splendor, but the story must match it. Fans on X are vocal: “RDJ as Doom is genius, but no script? Marvel’s playing with fire,” one wrote. Another gushed, “The Russos pulled off Endgame. I trust them to make this chaos work.”
Why Doomsday Could Redefine the MCU
Avengers: Doomsday is a high-stakes gamble, a $300 million bet that Marvel can turn chaos into triumph. Its sprawling cast, multiversal scope, and Downey’s villainous turn make it the MCU’s most ambitious project since Endgame. The unfinished script, while risky, reflects Marvel’s willingness to adapt, letting actors like Mackie, Hemsworth, and Downey shape their characters in real-time. Filming wraps in late 2025, with reshoots likely to refine the narrative. If the Russos can harness this energy, Doomsday could be a thrilling return to form, setting up Secret Wars as the MCU’s grand finale.
For fans, the anticipation is electric. Stream The Fantastic Four: First Steps and Thunderbolts on Disney+ to catch up, and brace for a multiversal showdown that could redefine superhero cinema. Avengers: Doomsday hits theaters December 18, 2026—will it be Marvel’s masterpiece or its messiest flop? Only time, and a finished script, will tell.
