Robert Downey Jr. returns to MCU as villain Doctor Doom.

Announcement made by Kevin Feige at San Diego Comic-Con.

Fans react with excitement and confusion over the casting news.

Russo Brothers to direct 'Secret Wars' and 'Doomsday' sequels.

Downey's Doctor Doom debut in upcoming Avengers film 'Doomsday.'

Fans debate if return undermines Iron Man's impactful death.

Multiverse concept allows Downey Jr. to play different characters.

Social media reactions mix nostalgia with skepticism and excitement.

Some fans view decision as a ticket sales strategy.

Downey Jr. made dramatic Comic-Con entrance in Doctor Doom costume.

Downey's performance as Iron Man sets high expectations for Doom.

Anticipation builds for Downey Jr.'s reinterpretation of Doctor Doom.