Robert Downey Jr. helped Marvel’s “Avengers” franchise skyrocket to success the instant he suited up as Iron Man in 2008. It’s a role he’s reprised in three films, with all four earning $3.9 billion in worldwide box office. He spoke to Variety’s Ramin Setoodeh about the franchise, his friendship with Chris Evans and, at age 48, how many more times he wants to suit up.

Had you met Chris Evans before he was cast in “Captain America?”

I have a vague memory of seeing him and whatever hot girl he was dating across from a dinner with me and Susan Downey. I think he and his girlfriend invited Susan and I back to their house to get in the Jacuzzi, to tell you the truth.

Seriously — did you go?

No, we did not, and by the way, like I said, that’s a vague memory, but that’s what I’d like for you to print.

Why did you urge Chris to take the Captain America role?

There was so much riding on what essentially could be considered the squarest superhero in history. It was probably the most risky of the franchises we launched. I say “we,” like I’m a company man, which I like to think I am. By the way, I’m a fan of his.

You are.

I’m not kidding. I’m having 50 kids over and I’m screening “Captain America 2” on my birthday, which happens to be the day it opens. I haven’t seen it. That’s one of the perks of being on the inside track at Marvel. I hope it’s not watermarked too heavily.

Were you nervous when they offered “Iron Man” to you?

Nervous? I was begging. I was absolutely certain it that would change my life.

There used to be a sense when you played a comicbook hero it could hurt your career.

Christopher Reeve went on and did a bunch of other great movies, and his notoriety from the “Superman” franchise helped that, and nobody held it against him. But the other thing is, everybody knows Chris Reeve was a really good guy. A lot of it has to do with personality. Are you the type of person who incurs ill will?

How many more of these Marvel movies do you think there can be?

The smart money is you have to look at everybody’s age. I’ll put myself at the top of the list. Sooner or later, they’ve got to start over and get somebody young. I’m not there with them yet. It really is the closest thing to being a beloved contract player with a big old-timey studio that there is right now. When you really think about it at the end of the day, these films are entertainment largely driven by young folks. There is something very honorable about that. I run into kids wearing “Captain America” masks. My kid believes that Captain America is real.

What’s a downside of playing a superhero?

It’s kind of like having a really cool TV job. They are always hoping they don’t get picked up for another season; or they are wondering if they’re going to get picked up for another season; or they have done so many seasons, and they are already sick of doing the show, but the show is so big, it’s working well for them. Any of those three things is better than calling your agent and saying, ‘Hey, anything going on? It’s pilot season.’ ”

You’re starting on “Avengers 2.”

This one is a very ambitious sequel. If you read it, it’s dense, it’s smart. Joss [Whedon] is a really smart guy. My 2-year-old is crazy about Hawkeye, and I think Jeremy [Renner] has a lot to do with the plot. There’s always so many plates to spin to get these things half-right, and I’m really excited about this one.