Marvel's most ambitious crossover yet, Avengers: Doomsday, is shaping up to be even bigger than anyone anticipated. Alan Cumming, returning as Nightcrawler after over two decades, has been making the rounds promoting his hosting duties on The Traitors and teasing a Romy and Michele's High School Reunion sequel. Somewhere between all that cheerful chatter, Cumming casually dropped something that sent the internet into overdrive, and Marvel's secrecy machine into full damage-control mode.

While Cumming cannot name the mystery returnee, the lengths Marvel took to hide this character suggest someone whose comeback would genuinely break the internet.

Avengers: Doomsday has at least one major unannounced character that Marvel is actively hiding from the public. Alan Cumming is reprising Nightcrawler, a role he last played in 2003's X2: X-Men United. The production used fake character names throughout the script to prevent leaks, a level of secrecy that goes well beyond standard Marvel protocol.

"They didn't want to let out this certain character was coming back, so they called them somebody else in the script," Cumming said in a Deadline interview.

Cumming then added, "It was so confusing," emphasising that even the cast members themselves struggled to track who was actually sharing the screen with whom, particularly since Cumming filmed numerous scenes in green screen isolation due to his The Traitors schedule.

The phrase "coming back" in Cumming's statement points firmly toward a returning face rather than a debut. Tobey Maguire's Spider-Man sits at the top of most speculation lists, given the multiverse framework and the precedent set by Spider-Man: No Way Home. Hugh Jackman's Wolverine, already resurrected narratively in Deadpool & Wolverine, remains another strong candidate. Famke Janssen's Jean Grey rounds out the shortlist, especially with Patrick Stewart, Ian McKellen, James Marsden, Kelsey Grammer, and Rebecca Romijn already confirmed, making her absence conspicuous.

Kevin Feige Breaks Down When ‘Avengers: Doomsday’ Takes Place in the MCU

As Marvel stacks confirmed names and hides others in plain sight, the CinemaCon trailer offered its own set of jaw-dropping reveals worth unpacking.

The CinemaCon trailer, shown in April 2026 but not yet released publicly, opened with Charles Xavier witnessing a catastrophic golden shockwave destroying the X-Mansion entirely. Robert Downey Jr. debuted as Victor von Doom in a throne room, projecting the kind of cold authority that made Thanos look impulsive. The Fantastic Four, led by Pedro Pascal's Reed Richards, formally met the remaining Avengers, with Richards explaining the mathematical certainty of multiverse collapse. Chris Evans returned as a bearded, long-haired Steve Rogers whose Endgame timeline decision appears directly linked to Doom's rise.

Beyond the headline moments, the Avengers: Doomsday trailer packed in Shang-Chi clashing with Gambit in a neon alley, Mystique infiltrating the Avengers by shapeshifting into Yelena Belova, and Wakandan Dora Milaje fighting Talokanil warriors in a flooded cityscape. Thor, voiced over much of the trailer with a weary prophetic tone, ultimately hurled Stormbreaker at Doom, who caught it bare-handed without flinching. With one secret character still hidden under a fake name somewhere in that ensemble, Cumming's offhand comment now reads less like a slip and more like the most interesting breadcrumb Marvel never meant to leave behind.

Marvel Boss Kevin Feige Stresses How Important Chris Evans and Robert Downey Jr. Are for ‘Avengers: Doomsday'

What are your thoughts on who Marvel's mystery returnee could be? Let us know in the comments.