How the 'Fantastic Four' Cast Became More Than Just Costars – Plus, Find Out Who's the Biggest Jokester on Set

"They were like siblings," the film's writer, Simon Kinberg, tells PEOPLE

Photo: C Flanigan/FilmMagic

It’s no secret the chemistry between Fantastic Four costars Miles Teller, Kate Mara, Michael B. Jordan and Jamie Bell is, well – fantastic.

The film’s screenwriter, Simon Kinberg, told PEOPLE at a fan screening in N.Y.C. on Tuesday that the cast became “a little family very quickly.”

“They were like siblings,” Kinberg said. “It was a lot of jokes and a lot of sort of cutting each other down all the time.”

Kinberg admitted Teller was the biggest jokester of the four.

“Miles by far, yeah. I mean all of them are pretty silly but Miles is the most consistently dangerous,” Kinberg said.

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Teller agreed that the cast had a lot of fun both on and off set, and they would often find themselves together at a bar in New Orleans when they weren’t working.

“All these actors have been working for a decent amount of time so I think everybody felt pretty comfortable. And when you’re doing a movie where the movie is so much bigger than you – I don’t know – it helps that there’s such a familiarity whether it be me with Michael, and Kate and Jamie knew each other for a long time.”

While Teller may be the biggest jokester, Jordan told PEOPLE Bell has the biggest heart.

“The guy is awesome,” Jordan said. “He’s very strong – he’s a protector and very protective about the people he cares about.”

Kinberg said the cast chemistry on the set of this film was similar to that of Brad Pitt and Angelina Jolie Pitt.

“I think it’s hard to fake chemistry. It goes back for me to Mr. and Mrs. Smith, which is the first film I ever worked on and it was like these two people are meeting for the first time and if you connect with somebody, you connect with them.”