Jack Black is 'diabolical, but in a fun way' as Satan in Dear Santa first look (exclusive)

It's been 10 years since Farrelly brothers Bobby and Peter last worked on a film together (Dumb and Dumber To) — but not for lack of trying.

They first heard the basic idea for their latest, the Christmas comedy Dear Santa, about 15 years ago, but the script just wasn't right. "It's a long-percolating movie, like all our movies," Peter explains to Entertainment Weekly. "By the way, Dumb and Dumber took five years to get made. There's Something About Mary was a 10-year-old script when we rewrote it. Kingpin was an old script when we rewrote it. They take a while to get there, and this was the case with this one."

It wouldn't have happened without Ricky Blitt (Loudermilk), who was the "driving force" behind getting the screenplay written alongside Peter, he says. Once they were happy with it, Bobby agreed to direct, and the rest is jingle bell history.

The holly jolly film follows young Liam Turner (Robert Timothy Smith), who still believes in Santa. To prove to all of his disbelieving friends that Santa is real, he writes a letter to the big guy inviting him to show himself. The only problem? Liam isn't a very strong speller and addresses the letter to Satan (Jack Black) instead. Satan, who never gets letters from kids, is flattered and goes to meet Liam. Hijinks, chaos, and hilarity ensue.

To cast this Satan/Santa, Bobby wanted someone who could play "diabolical, but in a fun way," and Black was the first and only choice. "Jack is just that guy that with his arching eyebrows and his faces and all that, there's a little bit of mischievous to him at all times, but he's eminently likable, and that's just Jack," says Bobby. "We never wanted to make it a horror movie or something like that. We wanted it to be comical. So it was a delicate ball of playing this iconic character but doing it in a way that the audience can have some fun with it. And Jack was the perfect guy."

So, as these things go, the Farrellys sent Black the script, and according to Bobby, the actor responded almost immediately to say he "was born to play this role" and even sent the brothers a picture of him dressed up in character to drive home the point. (Black's photo would later form the basis of the character's overall look in Dear Santa.)

The rest of the casting was a "home run," too, says Bobby, who shouts out his young cast (Jaden Carson Baker, Kai Cech) as much as the adults (Brianne Howey and Hayes MacArthur, who play Liam's parents, and PJ Byrne). The film also features Keegan-Michael Key in a, well, key, role.

"Keegan, anytime you can get him in a comedy, it's a home run. And I was just so happy when we had a role that I thought Keegan would be great for," says Bobby. "Keegan plays the kid's therapist, and he just as always knocks it out of the park and he comes with ideas, and he's just so much fun to work with."

Dear Santa also features a cameo by Post Malone, who plays himself. There's a scene in the film that calls for the kids to go to a concert, and Bobby says the artist was their top pick "because I love Post Malone, and I know that kids that age love Post Malone."

"So he played himself, which isn't the easiest thing for anyone to do, believe it or not, and sang a song. But he was great, and he was so much fun to work with. I would love to work with him again," the director adds of the singer.

It all amounts to a milestone of sorts for the brothers — Dear Santa is their first foray into a Christmas movie. But fans of their beloved comedies needn't worry about them straying too far from their usual sensibilities.

"It is a family story because it is Christmas. But you know what? Pete and I, we're the Farrelly brothers, so we wanted to put our skewed version on a Christmas story like this, but at the same time, we don't want to just blow it up. We wanted it to have a sweetness to it underneath all the edge and all that," Bobby says, adding, "so that's the Farrelly Brothers Christmas movie."

Peter warns that he doesn't think young kids who still believe in Santa Claus should watch the film, lest he and his brother be held responsible for bursting kids' bubbles, but otherwise, it's "100 percent family-friendly." As co-writer, his favorite part of the film is "the fantastic message" that comes through the movie, "because Liam has asked Satan to come accidentally, he gets to make some wishes, and it's about those and what he does with those, and who he becomes." And, he teases, "There's a nice twist at the end."

Still, viewers should expect to laugh around all the warm fuzzies. "It's funny as s---," Peter says. "It really is. It's got funny, funny stuff. It's a little edgier than a lot of Christmas movies, but it's not Bad Santa."

He continues, "I love Bad Santa. It's classic, but that's a different kind of movie. And this isn't that. Honestly, that'd be like comparing Dumb and Dumber to There's Something About Mary. This is the Dumb and Dumber version."

Ultimately, the brothers are thrilled for Dear Santa to finally be unwrapped — it got delayed on account of last year's writers' and actors' strikes. When EW speaks to Bobby and Peter by phone, it's the day before the U.S. election, and tensions in the world are high.

"Yeah, we need to laugh," Bobby says. "And comedy, in general, has sort of been on a hiatus, so I think it's going to be a good time to bring back just something to get people laughing and thinking about other things."

Want more movie news? Sign up for Entertainment Weekly's free newsletter to get the latest trailers, celebrity interviews, film reviews, and more.

Kevin Barnett, Pete Jones, Gretel Twombly served as executive producers, while the Farrellys and Jeremy Kramer produced the film. Featuring a screenplay by Blitt and Peter, with a story by Blitt, Peter, and Dan Ewen, Dear Santa hits Paramount+ and digital just in time for the holidays, on Nov. 25.