Though not boasting the bold-faced status of Thanksgiving and New Year’s Day, a variegated array of annual celebrations appears on the calendar – albeit in small print. One is International Ninja Day, which shares December 5th with a handful of other commemoratives, including National Sacher Torte Day and National Bathtub Party Day. This year, a band of children’s authors with recently published ninja-themed books have joined forces to organize Ninja Day Story Time, to encourage booksellers, librarians, and young ninja devotees to celebrate the occasion.

The Ninja Day observance was the brainstorm of Corey Rosen-Schwartz (Three Ninja Pigs and Ninja Red Riding Hood, both illustrated by Dan Santat, Putnam), who recruited five fellow picture-book authors to join the initiative. Other participants are Arree Chung (Ninja!, Holt), Jennifer Gray Olson (Ninja Bunny, Knopf), Rubin Pingk (Samurai Santa: A Very Ninja Christmas, S&S), Todd Tarpley (My Grandma’s a Ninja, illus. by Danny Chatzikonstantinou, NorthSouth), and Chris Tougas (Dojo Daycare and Dojo Daytrip, Owlkids).

The idea of a joint celebration of Ninja Day came to Rosen-Schwartz soon after the release of her debut book, The Three Ninja Pigs, in 2012. “It occurred to me then that cross-promotion was a win-win for everyone,” she recalled. “I did an event at Hooray for Books while on vacation in Alexandria, Va., and invited in a local dojo, Seichou Karate. The martial arts school invited all their students to the event, and it was such a big success that the bookstore and dojo now do joint events without me!”

Inspired by this enthusiastic response from ninjas-in-training, the author reached out via social media to other picture-book authors whose books star young ninjas. “I got to thinking about people I knew who had published awesome ninja books, and decided it would be fun to combine efforts and try to make Ninja Day into a big thing,” she said. “I enjoy doing the outreach, but I don’t have the design skills to create promotional materials, so I contacted Jennifer Gray Olson, an extraordinarily talented illustrator.”

Olson created the promotional image and tag line, “The Story Time You Never Saw Coming,” which is featured on Rosen-Schwartz’s website. Olson also designed the ninja name tags, activity sheets, and other downloadable items on the site, some of which are also included in the Ninja Prize Pack that booksellers, teachers, librarians, and dojos can order there. Olson emphasized that the authors’ complementary skills have made the initiative come together smoothly, noting, “Corey is a genius at conceptualizing ideas and marketing, and I am a more visual person, and came up with a cohesive design for the promotional materials. It was successful teamwork.”

Rosen-Schwartz and Olson both praised the contributions of another member of the team: Pingk. “Rubin took the graphics to a whole new level, by creating images featuring all of our characters combined,” explained Rosen-Schwartz. Among Pingk’s designs are a “Ninjas Read” picture of all of the books’ protagonists lined up at a library checkout desk, found on Twitter; as well as a “Got Ninja?” promotional poster portraying and identifying each book character, which he adapted as a coloring sheet.

Ninjas, Ninjas Everywhere

Though creatively drawn to the ninja theme for a variety of reasons, the authors’ book ideas had a common thread, to one degree or another: their own children. Rosen-Schwartz’s inspiration for The Three Ninja Pigs came over family dinner in a restaurant where their server’s first language was Spanish.

“When my four-year-old daughter told our server she could speak a little Spanish,” said the author, “my son Josh, then three, who was taking a martial arts class at his preschool, chimed in with, ‘I speak a little karate.’ That was my ‘A-ha!’ moment. Kids really are fascinated by ninjas, who are associated with stealth, speed, and strength. And what kid would not be enamored with the idea of going on a secret mission?”

Olson’s son also inspired her karate-themed book, Ninja Bunny, starring a rabbit whose ninja aspirations include flying. “My son Eli was seven when I first began my book,” she said. “His imagination knows no bounds, and on any given day he thought he could be an astronaut, a firefighter, or a ninja – and at one point he really believed he could fly! So the idea of a ninja bunny who thinks he can fly popped into my head.”

Pingk tapped into his own positive childhood memories of ninjas when he, quite serendipitously, conceived of Ninja Santa. “As a kid, I loved ninjas and the idea that sometimes, to get what we want, we have to be sneaky,” he said. “I loved anything related to numchucks or Ninja Turtles – as do my own kids. In 2013, I was out of work due to a government shutdown and, as I do every day, I began to sketch. And I found myself sketching ninjas chasing Santa, and then came up with a story about them, and went on to find an agent and a publisher.”

Pingk will celebrate this year’s Ninja Day with an appearance at The King’s English Bookshop in Salt Lake City, and Rosen-Schwartz and Tarpley will read their books at a story time at Manhattan’s Books of Wonder, where manager Scott Wong expressed optimism about kids’ ongoing interest in things ninja.

“There are certain book subjects customers ask for regularly, especially for boys: dinosaurs, trucks, and ninjas,” said Wong. “And the ninja-themed picture books that have come out lately tend to be a lot of fun, and make ninjas a lot more mainstream and cooler. The Ninja Turtles were certainly a part of my childhood, and I definitely don’t see a decline in ninja popularity.” Wong added that he’s hoping for a good turnout at his store’s Ninja Day story time, with good reason: “After all, who doesn’t love a ninja party?”

The participating authors have high hopes for the future of Ninja Day: plans for 2016 include adding more authors to the roster, launching a dedicated website, creating more activity ideas, and expanding promotional outreach. “We’d love to see bookstores, schools, and libraries celebrate Ninja Day in all 50 states and beyond,” said Rosen-Schwartz. “We are only just getting our efforts off the ground – the possibilities are endless!”