I mean, it sounds like a joke right? Like a desperate or cynical stunt to use his appeal to get the franchise going again … or is that just me?

I can see some multiverse thing about Doom being a dark version of Iron Man … that’s make sense and basically confirm the beliefs that RDJ’s iron wasn’t going to be gone for long. Even still, it’d appear cynical.

But in Hollywood, a major actor playing multiple roles in the same franchise, isn’t really a thing (for better or worse) … so this is certainly something right?

JFC, I had to check what community this was posted in. Omg, RDJ as Dr Doom!! This is really happening!!!

Infinity Rob

InfiniTony War

Apparantly there’s a multiverse with Tony becoming Dr Doom so… This could be interesting.

didn’t Tony Stark have a twin?

If I recall correctly, he has a corrupt time traveling nephew. And…

He’s had to fight his own corrupt future self at least twice. He’s been replaced by AI at least twice three times (I remembered a third).

And there’s alternate timelines where he becomes Sorcerer Supreme, and where he becomes Doom.

As Movie Bob says, ‘Comics are Weird’.

That would be a bit cheap, the best bet is this Doom is an alternate reality Iron Man.

Entertainment Weekly have been trying to piece the clues together:

Marvel directors Joe and Anthony Russo will be re-teaming with Downey for the first time since they killed off Tony Stark together in 2019’s Avengers: Endgame, but they did not divulge many details about their upcoming movies other than their titles. The fifth Avengers movie, initially called Avengers: The Kang Dynasty, has now been revamped to Avengers: Doomsday with a focus on Doom instead of Kang, while the sixth one will still be Avengers: Secret Wars. But the Russos did mention that introducing Doom into the MCU is essential preparation for the latter film, which gives a slight indication of what we’re in for here.

“It’s the biggest story that Marvel Comics ever told,” Joe Russo said on stage about Secret Wars. “It’s the reason Anthony and I are standing up here. It’s world-colliding epic-ness. But we need to make another movie first. There is one very important character that is required to do it justice.”

Secret Wars was a massive Marvel event comic, written by Jonathan Hickman with art by Esad Ribic, and first published in 2015. It tells an epic story of the multiverse getting destroyed by a process of parallel universes colliding into each other, thanks to the machinations of a group of powerful supernatural beings called the Ivory Kings. In that comic, Doom is able to save a small group of characters from across time and space and assemble them on a ragtag planet called Battleworld.

In other words, you can’t do Secret Wars without Doom, and if the post-credits scene of The Marvels is any indication, we won’t see an MCU X-Men movie without Secret Wars bringing parallel universes together.

Since Secret Wars is a multiverse story, that raises the distinct possibility that Downey’s Doom may by a multiversal variant of Tony Stark. That would be different than how variants have previously worked in the MCU, where they all share a common name or (in the case of the Deadpools from Deadpool & Wolverine) at least a costume. But then, Doom never plays by anyone else’s rules.

Introducing Doom in an Avengers movie is another surprise, since the character is usually the archenemy of the Fantastic Four — who, as it happens, are also making their long-awaited MCU debut soon. That movie is set to feature Ralph Ineson’s world eater Galactus as the primary adversary of the team, but since it’s set in a different universe than the main Avengers timeline, maybe Doom is that world’s equivalent of Stark. The fact that we’ll now have seen the character Reed Richards played by two different actors in MCU movies (John Krasinski in Doctor Strange in the Multiverse of Madness and now Pedro Pascal in The Fantastic Four: First Steps) may make it easier to accept the same actor playing two different characters.

So Secret Wars will see a lot of multiverse variants brought together by Doom, so it opens the door for him to actually be an alternate Iron Man. It may also be the key to bringing the X-Men and FF into the MCU or making it more viable to cross them over somehow.

It may even be we’ll see RDJ in the FF film, perhaps just a cameo or end-credit scene, as he would need some set-up before Avengers: Doomsday.

From IGN:

It’s also worth pointing out that there are versions of Doctor Doom in the Marvel multiverse who actually are Tony Stark. One of these is Iron Maniac, a version of Tony Stark introduced in 2004’s Marvel Team-Up #3. Another is featured in 2010’s What If? Iron Man: Demon in an Armor #1. In this world, Victor von Doom swapped bodies with Tony Stark in college. Trapped in his rival’s body Tony swears revenge and begins a yearslong quest to destroy Doom’s Stark Universal company.

I’d guess the What If? is the way they’d go.

Iron Man died. And with the multiverse stuff being the thing right now, this Dr. Doom is likely an alternative Tony Stark.

Because there are other actors who have appeared as different characters in Marvel movies… In fact, D&W contains at least two that I can think of and one is generating a few articles in my newsfeed, although I suspect you are referring to the other, which is indeed one of the best bits of the film (and the end-credit scene).