Gwyneth Paltrow and Mark Ruffalo react to Robert Downey Jr.'s return to Marvel

Gwyneth Paltrow and Mark Ruffalo have weighed in on their co-star Robert Downey Jr.'s return to the Marvel Cinematic Universe (MCU).

The Oppenheimer actor was dramatically revealed to be playing villain Victor von Doom/Doctor Doom in the upcoming Avengers movies Doomsday and Secret Wars during Marvel's panel at San Diego Comic-Con over the weekend.

It marks a sensational return for the Oscar-winning star, who famously played Tony Stark/Iron Man in the MCU between 2008 and 2019's Avengers: Endgame, when his character was killed off.

Paltrow, who played Stark's business colleague and love interest Pepper Potts in the Iron Man and Avengers films, appeared confused by his casting in the comments of Downey Jr.'s announcement on Instagram.

"I don't get it, are you a baddie now?" she commented.

Ruffalo, who plays Bruce Banner/Hulk in the franchise, told his co-star "green suits you", while directors Joe and Anthony Russo posted, "We've always said green is your color..."

During Marvel's Comic-Con panel over the weekend, it was confirmed that the Russo brothers would direct Avengers: Doomsday, which is due out in May 2026, and Avengers: Secret Wars, which will follow a year later in May 2027. They've previously helmed four MCU movies, including Avengers: Endgame.

Other Marvel stars learned of Downey Jr.'s new role while at Comic-Con themselves.

Florence Pugh, who plays Yelena Belova, appeared shocked at the news on the red carpet and told The Hollywood Reporter, "I hope I get to do a few scenes with him because I didn't get to do scenes with him in Oppenheimer. Let's figure that out!"

Anthony Mackie, who is the new Captain America, told the outlet he wants to be the one to defeat Doctor Doom.

"I better kill him first. I get first dibs to knock him off.... He's gonna pull a hamstring, I'mma take him down. I am not going lightly into that dark night," he declared.

Bucky Barnes/Winter Soldier actor Sebastian Stan called the news "exciting" and said, "It feels like something's right in the world again."