Mac Barnett and Jon Klassen, venturing far and wide to promote their new picture book How Does Santa Go Down the Chimney?, made an unusual stop on Elizabeth Street in Manhattan on December 2. The author-illustrator duo, Candlewick Press, and designer denim shop 3sixteen partnered for a winter event, where admirers of the books and the brand could buy exclusive T-shirts featuring the Shapes series characters from Barnett and Klassen’s Circle, Square, and Triangle.

For each of the 200 limited-edition tees sold, Candlewick donated a book to an elementary school in either New York or Los Angeles, 3sixteen’s retail locations. “Everybody—3sixteen, Candlewick, us—wanted there to be some charitable component from the beginning,” Barnett said, and 3sixteen’s Johan Lam suggested the one-for-one donation. Because the Santa book is holiday-specific, the donated books include Barnett/Klassen collaborations such as the Shapes trilogy, The Wolf, the Duck, and the Mouse, and Sam and Dave Dig a Hole, plus titles by Kate DiCamillo, Meg Medina, and Nigerian-born creator Atinuke.

Klassen and Barnett bonded with 3sixteen co-owners Lam and Andrew Chen over a shared appreciation for craft and for clothes as “emotional objects,” Barnett said. This isn’t fast fashion: the heavyweight jersey for 3sixteen’s T-shirts is knit in Canada, then cut and sewn in the San Francisco factory that makes their premium raw denim jeans. “We love their clothes, and we found out they love our books,” Barnett added. “We’ve found a real kinship in our approaches to constructing things that have integrity and meaning.”

3sixteen’s owners are fathers, which facilitates the “mutual admiration,” Lam told PW. “Andrew and I both have young sons, and rich storytelling and art quickly rise to the top of the books that you reach for. Mac and Jon’s stories have become a big part of our kids’ childhoods.”

The four friends’ conversations turned to an in-store book event for December, outside the norm for the NoLita boutique. “Most of our events, like most fashion parties, aren’t really geared toward families,” Lam said, but “we have a ton of customers who are fathers of young children and are also fans of Mac and Jon’s work.” A holiday-themed book signing would welcome all ages to the menswear atelier.

Barnett and Klassen were game. “Jon and I like reading our books in unexpected places, and we think it’s cool that some of the guys who shop at 3sixteen can take their families to this place they love,” Barnett said. They made one small request: “Jon and I asked if they might want to do a shirt with us.”

Notwithstanding that he and Klassen are kind of a big deal among the picture book set, “we were a little nervous,” Barnett admitted. “3sixteen’s T-shirts are famous, Andrew and Johan’s sense of graphics is excellent, and the brand’s collaborations are legendary.” As luck would have it, “they were immediately up for it, and we had a lot of fun cooking up these shirts together.”

At the morning event, 3sixteen’s Chen dressed as Santa for photo ops, while Lam, Barnett, and Klassen decked the halls as elves in green and gold. Guests enjoyed cocoa and coffee, and despite the holiday getups, no one summoned the fashion police.

On December 9 and 10, Barnett and Klassen will headline holiday events hosted by Mr. Mopps’ Children’s Books and Toys in Berkeley, Calif., and at the Ferry Building in San Francisco.