John Krasinski Is Down for 'The Office' Spin-Off Cameo: 'Done!' (Exclusive)

“Extra” chatted with John Krasinski at the “Fountain of Youth” NYC premiere at the Museum of Natural History.

In the movie, John and Natalie Portman play siblings on a mission to find immortality.

John, who shares daughters Violet and Hazel with wife Emily Blunt, revealed the children got to come to set!

He confessed, “They came on the Vienna set in the library, so they got to see Eiza [González] beat the living hell out of me — and I think they like that a little too much!"

Krasinski also praised director Guy Ritchie, saying, “I think Guy changed the way we make movies. I think that the way he shoots, the way he looks at the world, is so unbelievably unique, and I would have done absolutely anything. I would have played a waiter. So, the fact that he asked me to be the lead in a movie with Natalie Portman, that was the easiest yes I've ever had.”

Stanley Tucci, who is married to Emily’s sister Felicity, is also in the movie, and John revealed, “I took Stanley as my date when we went and had dinner at Guy's house the first night, and then they fell in love and then [Guy] told me, ‘Yeah, so Stanley's coming in to shoot tomorrow.’ And I went, ‘What? In this movie?’ And he went, ‘Yeah, yeah.’ No one told me anything.”

Meanwhile, Stanley and Emily are both starring in the upcoming “Devil Wears Prada” sequel. John told us, “They haven't spilled the beans at all, and I don't want them to because I just want to see the movie.”

Plus, John reacted to “The Paper,” a spin-off of “The Office” starring his “Fountain of Youth” co-star Domhnall Gleeson, saying he's down for a cameo!

“I'm excited to see what they do with it. It's such an amazing idea, and listen if Greg [Daniels] is behind it, we're all in. And you can't get a better actor than [Domhnall] to take on the mantle. He's so, so great. He's going to be so perfect for it, and we'll probably start doing watch parties again just to watch them.”

When asked if he would consider a cameo, John insisted, “Done! If they ask me, I’m in.”