Robert Downey Jr. hails original X-Men stars' return in 'Avengers: Doomsday'

Robert Downey Jr. has shared his excitement over the return of the original X-Men cast to Avengers: Doomsday, admitting the veteran Marvel stars created an unforgettable atmosphere on set.

Speaking during Entertainment Weekly's post-Hall H interview at San Diego Comic-Con, the actor—who is set to portray Doctor Doom in the upcoming Marvel blockbuster—praised Rebecca Romijn and Kelsey Grammer for reprising their iconic roles as Mystique and Beast.

"It was a big moment, you and Kelsey being back," Downey told Romijn before revealing that the cast "nerded out" over the pair's return.

Although he avoided revealing any story details, Downey said having the original X-Men stars on set "lit up this constellation of excitement," calling the experience "just incredible."

Romijn and Grammer last appeared together in significant X-Men roles in 2006's X-Men: The Last Stand. Grammer later made a post-credit appearance as Beast in 2023's The Marvels, while Romijn briefly reprised Mystique in X-Men: First Class.

Avengers: Doomsday will also reunite several other original X-Men actors, including Patrick Stewart as Professor X, Ian McKellen as Magneto, James Marsden as Cyclops and Alan Cumming as Nightcrawler, rather than the younger versions portrayed in later X-Men films.

Reflecting on his return as Beast, Grammer said he has always admired the character's nobility and compassion.

"I love the character," he said, explaining that Beast represents goodwill and the belief that goodness ultimately prevails.

Meanwhile, Romijn admitted she was relieved the makeup process for Mystique was much faster this time around. 

However, she joked that the lengthy transformation in the original films helped her get into the right mindset to portray the fierce mutant.

Avengers: Doomsday is scheduled to arrive in theaters on Dec. 18, 2026.