When did you know you wanted Ultron as the villain for this movie?

Before I took the first movie. For me what was interesting is that he is this angry, and I hired the smoothest talker in Hollywood to play him. I did it on purpose. I needed a guy who can give you the Morpheus but then can just LOSE HIS SHIT. Spader’s really good at that and he’s really good at finding the darkness, but also the comedy. The comedy is always a huge thing for me. Tom Hiddleston is hilarious. Hiddleston can turn on a dime, which is my favourite thing. He can be absolutely apocalyptic and then, ‘Um, point of order?’ Ultron has the same thing. He is very different, obviously, in his rhythms and his concepts, but for me it’s a guy who’s that angry and who hates the Avengers that much and is also a robot and is therefore going to have every issue that a robot’s going to have with humanity anyway… there’s a lot to play there. For me, he’s an iconic figure.

Did you play around with his powers, and what he’s capable of?

Yeah, I did. The powers in comic books – they’re always like, ‘And then I can reverse the polarity of your ions!’ – well, we have to ground things a lot more. With Ultron, we have to make him slightly less omnipotent because he’d win. Bottom line. Also, having weaknesses and needs and foibles and alliances and actually caring what people think of him, all these things, are what make him a character and not just a tidal wave. A movie about a tidal wave can be great, but it’s different than a conflict between one side and the other.

When Ultron speaks, he has a point. He is really not on top of the fact that the point he’s making has nothing to do with the fact that he’s banoonoos. And that he hates the Avengers for bringing him into this world, and he can’t really articulate that or even understand how much he hates humanity. He thinks he all that. That guy is very fun to write. He combines all the iconic stuff. The powers he has are slightly different – he can control certain things, he’s not just firing repulsors.

And you also have Quicksilver and Scarlet Witch.

They have an origin but it’s largely described. They’re already good to go by the time we’re up and running. You don’t want to fall into Spider-Man 3 territory – and I say that as a guy who actually thinks pretty well of that movie, there’s some great stuff in that movie – but there comes a point where you’re overloaded with frontstory, backstory, origin story and it becomes very hard to juggle. My instinct is always, ‘Don’t put in more, work with what you have.’

But I insisted on putting in more in this movie because I felt I needed more villains. I needed someone for Ultron to talk to, and I need more trouble for the Avengers. As powerful as Ultron is, if he builds more Ultrons, they’re Ultrons. There’s no reason for him to ever to talk to them because they’re him. ‘I need you to – I KNOW! I AM TOTALLY YOU! I DID IT EARLIER! I know that because I am also me.’ That’s not a good conversation. Actually, it sounded pretty good there. I think I’m onto something.

You’ve retconned Ultron’s origin. In the comics, Hank Pym – Ant-Man – creates Ultron. Here, it’s Tony and, to a lesser extent, Bruce.

Of all the heat I’ve ever taken, not having Hank Pym was one of the bigger things. But the fact of the matter was, Edgar had him first and by virtue of what Edgar was doing, there was no way for me to use him in this. I also thought it was a bridge too far. Ultron needs to be the brainchild of the Avengers, and in the world of the Avengers and the MCU, Tony Stark is that guy. Banner has elements of that guy – we don’t really think of him as being as irresponsible as Tony Stark, but the motherfucker tested gamma radiation on himself, with really terrible, way-worse-than-Tony-Stark results.

It didn’t make sense to introduce a third scientist, a third sciencetician, to do that. It was hard for me, because I grew up on the comics, to dump that, but at the end of the day, it’s a more interesting relationship between Tony and Ultron if Tony was once like, ‘You know what would be a really great idea?’ They’re doing what they always do – which is jump in headfirst, and then go, ‘Sorry, world!’ But you have to make it their responsibility without just making it their fault.