It’s probably not giving too much away about the forthcoming, hyped-to-the-ether Flash movie to reveal that it plays heavily, and with great joy, on famous “almost were” castings as it delves into the multiverse. Warner Bros/DC has already confirmed that Nicolas Cage will appear briefly as Superman in Andy Muschietti’s comic book epic.

Perfect timing, then, for us to discover an all-new sliding doors moment that might have changed the face of the rival Marvel Cinematic Universe. In a new video celebrating the 15th anniversary of Iron Man, director Jon Favreau reveals that star Robert Downey Jr was in earlier talks to play the villain Doctor Doom in the deeply average Tim Story-directed Fantastic Four (2005). In the end, the role went to Nip/Tuck’s Julian McMahon, though if you remember that, it’s probably because you’re primed and ready to go on Mastermind specialising in “obscure superhero movies” .

It’s not impossible, given how rapidly the Marvel setup was changing in the 00s (from hands-off rights holder in the early part of the decade to fully fledged mini-studio by the end) that Downey Jr might still have wound up taking the role of Iron Man. After all, Story’s Johnny Storm/Human Torch, Chris Evans, ended up being cast as Captain America in the MCU, and lasted for many years. It’s also possible that taking the role of lead villain in what turned out to be one of the feeblest comic book movies of the era might have scuppered Downey Jr’s career altogether, given the actor’s well-publicised struggles during the period immediately before his casting as Tony Stark.

Might this be the latest “almost was” moment to end up morphing into reality, thanks to the multiverse? Probably not, but it’s certainly fun to imagine, and stranger things have no doubt happened in the last five seconds in this brave new era of comic book stunt casting. Marvel already gave us John Krasinski as Reed Richards/Mister Fantastic in an alternate version of reality visited by the one-time sorcerer supreme in Doctor Strange in the Multiverse of Madness, largely because fans had clamoured for the casting. Some were hoping to see Tom Cruise as Tony Stark/Iron Man, but you can’t have everything.

Or can you? Marvel’s version of the multiverse would certainly allow Downey Jr to appear as Doctor Doom in the forthcoming, Matt Shakman-directed Fantastic Four reboot. And if you’re going to roar back to the MCU after playing such a huge part in its success, then surely doing so as a high-profile villain – one that’s never been adequately represented on the big screen – would be the perfect resurrection.

The only issue is that Marvel would no longer have the option in its back pocket of restoring Downey Jr as an alternate reality version of Stark in a future movie. And you just know that’s got to be lurking somewhere in the dark corners of the MCU writers’ room, a button to be pushed when times get really tough (or several Marvel movies in a row fail to score at least a billion dollars at the box office.)

Then again, Ezra Miller is said to be superb as two different versions of Barry Allen (who share the screen for much of the film’s run-time) in . So why not double down on Downey Jr and let him play both roles?

Madness you say? Hey, DC just put Cage back in his Superman suit, and Michael Keaton is about to soar across the Gotham skyline once more as a septuagenarian Batman. There are other Easter egg moments in The Flash that will put your eyeballs on stalks. In the modern era of the comic book movie multiverse, all bets are off.