David Harbour recently discussed his experiences of working on the set of Marvel’s Avengers: Doomsday and collaborating with directors Anthony and Joe Russo, and their “special sauce”, Collider reports.

First appearing in 2021’s Black Widow as the titular character’s adoptive father, Alexei Shostakov, a.k.a. Red Guardian, Harbour shortly returned to voice an alternate universe version of the character in the third season of Marvel’s animated streaming anthology, What If… He next appeared in this year’s Thunderbolts*. Now, Harbour is strapping on the red costume once again for the upcoming Avengers: Doomsday.

While no stranger to comic book movies, having starred in 2019’s Hellboy, Harbour has called working on the Marvel Cinematic Universe entry an extraordinary experience, saying,

“I was not even convinced when we started, and this movie’s gonna be really good…I will say I’ve never been on a set like this in my life. I’ve never seen anything like this…It’s just insane to look around the room and be like, “Oh my god, I’m in the movie. There’s what’s his face doing that speech. It’s just enormous.'”

The actor also touched on his experience of being directed by the Russos:

“They have a special sauce. I don’t even really understand, but they just know how to do these things…there’s something about the layers in which they put the comedy and the drama and the surprises and the scale and the epicness and all that stuff. It’s incredible.”

As Red Guardian, Harbour will reunite with his castmates from Thunderbolts*, Florence Pugh, Sebastian Stan, Wyatt Russell, Hannah John-Kamen, and Lewis Pullman, and be featured in an all-star ensemble cast of 27 characters that includes The Avengers, The Fantastic Four, The X-Men, and more, facing off against Robert Downey, Jr’s villainous Doctor Doom.

Avengers: Doomsday is scheduled for release on December 18, 2026.