Marvel boss Kevin Feige says the MCU would be nothing without Robert Downey Jr.

Everyone will have a favorite Marvel superhero but it's clear Kevin Feige has his favorite MCU actor.

He's gone on the record to state the Marvel Cinematic Universe would be nowhere without Robert Downey Jr.

The actor helped kickstart the juggernaut that its beloved around the world when he signed on to play Tony Stark in the first Iron Man film.

That was all the way back in 2008 and when Marvel saw how successful it became, it was a no brainer to keep it going with other superhero films.

There have been more than 30 films since that origin story and more than 20 TV shows across five phases.

To celebrate Iron Man's 15th anniversary, Marvel boss Kevin Feige and director Jon Favreau have reflected on how everything started when Downey Jr. agreed to star in the film.

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The director said: “Once it was Robert, then every decision became a lot easier.

“I remember sitting down with [Robert] and I was like, he just got it and he's got that spark in him and his eye and he's ready."

Feige added: "I remember on later movies – we’ll talk about them on the 15th anniversary of those – there were dark days.

"I would say to Robert, ‘We wouldn’t be in this mess if it wasn’t for you', meaning we wouldn’t have a studio if it wasn’t for him. Or you [Favreau]."

They both remarked how RDJ helped make superhero movies cool for big name actors.

Marvel was able to bring in the likes of Paul Bettany, Chris Evans, Scarlet Johansson and others who would have normally been doing other genres.

But Downey Jr. wasn't a new face for the emerging Marvel machine. Favreau has confirmed the actor screen tested for another movie.

He recalled: "Robert had come in for a general on it and I remember you had all met with him already for like Dr. Doom or something on another project... I think he had come through on... like Fantastic Four.

"So everybody sort of knew who he was...and that's when we were in your [Kevin Feige's] office and we were pointing to his headshot and saying we got to try to figure this out."

We bet they're lucky they ended up going with the actor to kickstart their humungous cinematic universe.

Cinema hasn't been the same ever since (whether you like that or not) and Marvel isn't showing any signs of slowing down.