David Harbour May Have Just Spoiled a Major Tony Stark Twist in Avengers: Doomsday

David Harbour may have accidentally revealed a major moment from Avengers: Doomsday.

The Stranger Things star will return as Alexei Shostakov, also known as Red Guardian, in Marvel’s upcoming crossover film. Harbour has mostly avoided revealing details about the movie, but a recent interview with Variety may have changed that.

During the interview, Harbour was asked to say one line from Doomsday without explaining the context. He responded in Red Guardian’s Russian accent: “You… are Tony Stark.”

The comment could simply have been a joke. But if Harbour was actually quoting a line from the movie, it may point to a major twist involving Robert Downey Jr.

Downey is returning to the Marvel Cinematic Universe in Doomsday, but not as Tony Stark. He will play Victor Von Doom, the villainous Doctor Doom. His casting surprised fans because Downey’s Tony Stark died in Avengers: Endgame, and Marvel had previously given no indication that the actor would return in another role.

One possibility is that Doctor Doom eventually removes his mask and Red Guardian recognizes him as Tony Stark. Since Downey played Stark for years, the moment could be designed to shock both the characters and the audience.

That could also suggest that Victor Von Doom is connected to Tony Stark through the multiverse. Doomsday is expected to bring together characters from several different realities, making it possible for familiar characters to have alternate versions of themselves.

Another possibility is even more dramatic: Tony Stark himself could appear.

Because the movie involves multiple universes, there could theoretically be another version of Tony Stark who survived events similar to those seen in the main MCU timeline. Harbour’s line could therefore refer to a multiversal Tony rather than Doctor Doom.

There is no confirmation that either theory is correct. Harbour could have been improvising, joking with the interviewer, or deliberately trying to mislead fans.

Still, his unusual choice of words has given Marvel fans plenty to speculate about. If “You… are Tony Stark” is genuinely part of Avengers: Doomsday, the line could reveal that Downey’s return has a much deeper connection to his former MCU character than Marvel has officially acknowledged.

Avengers: Doomsday is scheduled to arrive in theaters on December 18.