Downey Jr., who spent over a decade portraying the beloved superhero Iron Man, last appeared in 2019's "Avengers: Endgame," where his character heroically sacrificed himself to save the universe. His return marks a significant shift as he transitions from hero to villain.

Making a dramatic entrance at the Comic-Con panel, Downey Jr. appeared on stage in an olive-green robe surrounded by individuals wearing Doctor Doom's iconic metal mask. He then removed his mask to reveal his identity, eliciting wild cheers from the audience. "New mask, same task," Downey quipped to the excited crowd.

Who is Doctor Doom?

Robert Downey Jr., best known for his iconic portrayal of Iron Man, will step into the shoes of another Marvel character: Doctor Doom. The character has previously been portrayed on screen by Julian McMahon in the 2005 "Fantastic Four" movie and Toby Kebbell in the 2015 reboot. The character also played a significant role in Marvel's 2015 "Secret Wars" comic, where he creates Battleworld, a planet where various universes collide.

Introduced in a 1962 issue of "The Fantastic Four," Victor Von Doom, also known as Doctor Doom, is a genius scientist from the fictional European country of Latveria. He is famously the arch-nemesis of the Fantastic Four’s Reed Richards, whom he first met as a student.

In the comics, Von Doom is disfigured by an explosion from one of his inventions, leading him to don a mask and suit of armor. He eventually becomes the ruler of Latveria and pursues global domination, driven by a desire for power and recognition. According to Marvel.com, "Whether he's using time travel, making deals with demons, or even teaming with his enemies to fight a common foe, Doom's endgame is to be the one in charge." He also has a mastery of magical spells.

This storyline could potentially serve as inspiration for the upcoming movie "Avengers: Secret Wars."

Is there a connection between Iron Man and Doctor Doom?

Ever since Marvel announced a new "Fantastic Four" movie, fans anticipated Doctor Doom's arrival in the MCU. However, the decision to cast Downey, who famously portrayed Iron Man, as Doom was unexpected. The specifics of how this will unfold remain unclear.

"The Fantastic Four: First Steps," set to release in 2025, takes place in an alternate universe. This suggests that Downey's Doctor Doom might originate from this alternate timeline, possibly as an evil version of Tony Stark.

There are also speculations that Doom could merely resemble Stark without being directly connected to him. If Doom's identity remains hidden behind his mask, Downey's portrayal might be disguised enough that his involvement isn't immediately obvious.