Cast member Robert Downey Jr. attends a premiere for the television series "The Sympathizer", in Los Angeles, California, U.S [Source: Reuters]

Robert Downey Jr. stunned fans as he removed a mask during Saturday’s San Diego Comic-Con Hall H panel, revealing that the “Iron Man” actor will rejoin the franchise as one of Marvel’s biggest villains Doctor Doom.

The panel was flooded with hooded figures concealed by masks that resembled the iconic comic book villain known for his skills in both sorcery and science when Downey Jr. revealed himself.

The Russo Brothers, who are returning to direct both “Avengers: Doomsday” and “Avengers: Secret Wars,” believe that while Downey Jr. has a “new mask,” he, the rest of the Marvel team, and everyone else has the “same task” of helping to “create the greatest possible experience” at the movie theatre.

Another major villain joining the Marvel Cinematic Universe is cosmic entity called Galactus, which will be the antagonist of “The Fantastic Four: First Steps,” and directed by “WandaVision” director Matt Shakman.

The panel had plenty more showstopping moments, as it began with a boisterous “Deadpool choir,” inspired by the recent film “Deadpool and Wolverine,” which Marvel president Kevin Feige said set the box office record for the highest-grossing R-rated film ever on Saturday.

Different iterations of the silly red-costumed character named “Deadpool” danced around the Hall H floor, walking amidst the seated attendees as the film’s anthem “Like a Prayer” by Madonna played.

The cast of the upcoming film “Captain America: Brave New World,” later joined the stage with lead Anthony Mackie sharing how his version of the titular superhero is different from actor Chris Evans’ version.

Following that “Indiana Jones” actor Harrison Ford, who replaces William Hurt’s role as antagonist ‘Thunderbolt’ Ross, joined the cast and playfully “hulked out” with his arms out and mouth open and then chased Mackie around the stage

David Harbour later walked into Hall H amidst the seated audience members wearing the costume for his “Black Widow” character named Alexei Shostakov.

He approached the stage to address the other cast members of the “Thunderbolts,” which centers on a team of Marvel anti-heroes, with a monologue complaining about them ignoring his idea for them all to dress up for the film.