The MCU is known for its tight security, with its cast and crew tasked with guarding the secrets of each upcoming Marvel movie and TV show. All eyes are on what The Russo Brothers have up their sleeves for Avengers: Doomsday, and Sebastian Stan is shocked that Chris Evans was confirmed to return as Captain America. As a fan who has spent years watching the Marvel movies in order I have to agree.What we know about Avengers: Doomsday is extremely limited, and the return of Steve Rogers is one reason why anticipation is so high. Chris Evans wasn't originally included in the Doomsday cast list, but we've already seen footage of his return as Captain America. In a clip from Happy Sad Confused podcast host Josh Horowitz's Instagram, Stan got real about his reaction to this reveal, offering: I can't believe that it's public knowledge that he's in the movie now... I was laughing because he was shooting in the movie and they had him isolated to a house, in a home far away like James Bond or something Ouch. Chris Evans might be making Marvel fans' days by returning as Steve Rogers, but the reality of filming Doomsday sounds super isolating. His role was top-secret, which meant he had to be housed away from the movie's announced cast. News of his role broke the internet, so maybe it was worth it. Still, Sebastian Stan is shook that the studio revealed his role so long before it actually arrives in theaters this December.Avengers: Doomsday's trailer showed some brief footage of Steve Rogers, who is wearing casual clothes rather than a Captain America suit. Luckily he'll be wielding Mjolnir, which he famously did in Endgame's final battle. Later in the same interview, Stan revealed a conversation he had with Evans about his surprise role, saying: I go 'How are you doing? Because no one can know you're in England for this long period of time. And how are you doing it?' It felt like a great secret.I don't know about you, but I'm dying to hear Evans' recollection of shooting Doomsday. It would have absolutely gone viral if his role was revealed, but the studio was able to control that narrative. Although Sebastian Stan is still shocked that his inclusion was revealed so long before the next Avengers movie was released. (Image credit: Marvel Studios)Fans are eager to see how the MCU's heroes will react to Steve Rogers' return, especially Anthony Mackie's Sam Wilson and Sebastian Stan's Bucky. The latter actor didn't reveal what's going to happen when they reunite in Doomsday, but he did speak about the unique challenge of bringing his signature character to life in the crossover event. In his words: But it's interesting because, again, you're always finding new levels of the character when they're opposite different people. I just sort of realized at the halfway point I was like 'I think I'm like Clint Eastwood in this group.' Meaning I'm just the guy in Unforgiven. The older, bitter guy that gets pulled in. This sounds like a funny dynamic, and I'm suddenly even more excited to see how Bucky interacts with the entire teams of heroes that will be part of Doomsday. Namely The Avengers, The Fantastic Four, the X-Men, and the New Avengers aka Thunderbolts. He's currently part of the lineup for the latter, but Bucky's got history with plenty of other characters as well.All will be revealed when Avengers: Doomsday hits theaters on December 18th as part of the 2026 movie release list. Hopefully Sebastian Stan's character doesn't get killed off so we can see more of his dynamics with the rest of the shared universe's heroes.