Tilda Swinton's Ancient One will make an appearance in Avengers 4. Executive producer Michael Grillo revealed that bit of news during a panel at The Austin Film Festival with screenwriters Christopher Markus and Stephen McFeely. The Ancient One was killed off in 2016's standalone Doctor Strange film, so Marvel Cinematic Universe fans are wondering how she will be brought back for the epic movie. While it's still unclear how the dusted characters will return, it's believed that time travel or flashbacks will be utilized.

MCU fans have wondered if Tilda Swinton's Ancient One would make an appearance in Avengers 4 ever since the release of Infinity War back in April. Nobody knows the Time Stone like the Ancient One. She has studied the Infinity Stone for several years, and if the movie is going to involve time travel, the Ancient One is definitely the character to help with that predicament. Michael Grillo accidentally revealed that Swinton is in the movie, after talking about how hard it was to get all of the actors on the set. He said, "When we got Tilda Swinton, she was just a 1-day availability."

Avengers 4 is probably the most mysterious film in the MCU. We don't even know the official title for the sequel yet, which has turned into an impressive guessing game for hardcore fans who analyze every little tease that the Russo Brothers release. Thankfully, Marvel Studios boss Kevin Feige has revealed that the first trailer for the film will be unveiled within the next few months, which should give us some more hints about how the movie will unfold when it hits the big screen.

Related: Marvel Launches Official Avengers 4 Countdown Clock

The Quantum Realm will be utilized in Avengers 4, but it's not clear how it will work. It's yet to even be confirmed that time travel will play a role in the movie, but set photos have teased that element in the past. Frank Grillo did recently confirm his role as Crossbones, and that flashbacks will be used to bring him back. For now, fans are left to speculate and come up with fan theories that are more fun than anything. With that being said, the mysterious Quantum Realm is rumored to play a major part in getting the universe put back together after the events of Infinity War.

Since Tilda Swinton is making a return, what other surprises are going to be hidden in Avengers 4? Aaron Taylor-Johnson's Quicksilver is another character who has rumored. However, Taylor-Johnson has hinted pretty hard that he will not have any involvement with the film, which is strange since he was spotted on the Atlanta set last year. Marvel Studios is doing a great job of keeping everything under wraps like they normally do, but Avengers 4 is a whole new level of secretive that is keeping MCU fans all over the world on the edge of their seats. This news was first reported by Super Bro Movies.