The Tonight Show Starring Jimmy Fallon has Christmas in mind all year round.

Mario Martines, the show’s costume department head designer, does anyway.

Martines and his team are the ones responsible for creating the 12 Days of Christmas Sweaters pieces, and all the beautiful, over-the-top ideas start as simple ideas in Martines’ head. And the team spends the entire year (in between other projects) bringing those sweaters to life just ahead of Christmas.

This is the show’s 12th year of the tradition, and every year is more extravagant than the last.

Christmas sweater.Credit: Todd Owyoung/NBC

Credit: Todd Owyoung/NBC

Credit: Todd Owyoung/NBC

“What I do is I do little scribbles of drawings right after the New Year,” Martines tells PEOPLE from inside his office at Rockefeller Center. “I don’t really know what they mean, but I’ll put scribbles down and then I’ll start elaborating on that. Then I will share it with my team. They think I’m crazy. But then they all go into action. I have a great team.”

Martines explains that all the sweaters start as just that: sweaters. He spends a lot of time looking for the “right base” to build the sweater from. He thinks about everything from the material to the color and how it can be transformed into a festive piece.

“When we first started doing this, they were just ugly sweaters or sweaters that were just found online. They were old, vintage things. And I knew in my head that they could be something more,” he shares.

“Something more” is an understatement when you look at the flashy designs on display during this year’s show.

One of this year’s sweaters is a Christmas Carousel — complete with lights.

“This whole thing lights up,” Martines says while showing off the piece. “I had this idea that I wanted a Christmas carousel, and it was in my mind, but I didn’t know what it meant really. Then I was watching this Italian crime show on Netflix, and they would meet every day. The lead detective would talk to this guy who would give her information by a carousel. And I was like, ‘I got to do this.'”

The sweaters aren’t just created to be shown off on Jimmy Fallon’s show, though. For each night of the 12 Days of Christmas Sweaters, Fallon reveals a garment to his studio audience. Then a number is drawn out of a Santa hat that corresponds to a seat in the audience, and that person gets to take the sweater home.

In one of this season’s episodes, the sweater was won by a teenage girl who is a Fallon superfan. It just so happens that she got to take home the first sweater that Martines started fashioning for this year.

“That one was where I had an idea of people shopping in a mall and going up and down escalators full of packages. That was the first one I really got my head around,” he says of the light-up piece that featured holiday shoppers.

Inside Martines’ Tonight Show office are binders with sketches and photos of all the sweaters he’s created over the years. While flipping through the collection, Martines reminisces about how all the garments came together.

“I’ll wake up in the middle of the night and just start sketching,” he says while pointing out some small designs that turned into elaborate sweaters. “I get my inspiration from anything. Normally, I have an idea, and I’ll scribble it down and then start doing sketches. But then sometimes what I’ll do is I will see a sweater that isn’t a Christmas sweater, and that’ll inspire me. So I work in the reverse sometimes.”

Somehow, even after more than a decade, Martines manages to continue coming up with new ideas. He gets a thrill each year when everything comes together and the sweaters make their debut on the show. He gets to delight the fans — and Fallon himself, who Martines says continues to be happy with their celebration.

“I’m really proud of them,” he says of the sweaters. “They became like a piece of art, each one.”