A pompom here, a knitted ornament there, Everett has been hit by a yarn bomber.

“I just wanted to spread some Christmas cheer,” Renee Walstad said.

Walstad is part of a warm-and-fuzzy movement being embraced by creative types all over the world.

Her efforts are modest compared with the ways some yarn artists decorate public places. For some yarn bombers, what began as a covert operation has blossomed into commissioned public art projects.

Since early this month, Walstad, 28, has been putting knitted and crocheted decorations on Everett’s downtown sculptures. She calls it a “Yarnvent calendar.”

“You know, like Advent,” the Lake Stevens woman said. “Every day before Christmas, I put up an ornament.”

If you stopped for coffee on Everett’s Colby Avenue on Wednesday, you may have noticed Walstad’s cheery calling cards. Near the Starbucks shop, the statue of three little girls holding hands — Georgia Gerber’s “Along Colby” — finds the girls dressed for the season in knitted red and green anklets. One of the bronze figures held a knitted Christmas ornament.

Walstad plans to put up her last yarn piece Saturday, on the steel “Braeburn Pear” sculpture outside shops on Colby. She promises to take the pieces down after Christmas.

“Some people take them and put them on their own trees. Whatever happens happens,” she said.

On Tuesday, in the late afternoon chill, Walstad was joined by several children from Everett’s Refuge Foursquare Church, where she is a member. Some of the kids had helped make the yarn doodads they put on several Wall Street sculptures.

They decked out “Balancing Big,” Joseph Kinnebrew’s sculpture of stacked red boxes outside the Monte Cristo building. When they finished, the metal sculpture looked like giant gifts tied up with string.

Cassie Smith, 12, of Lake Stevens, described making a finger-crocheted rope. “You tie a knot around your thumb, and twirl it around, and twirl it around,” Cassie said.

“It’s a little Christmas adventure,” said Heather Mitchell, whose 16-month-old son Elijah and 3-year-old daughter Kirsten were part of the decorating crew.

In some places, yarn bombing is a big adventure.

The phenomenon was explained in a 2009 book, “Yarn Bombing: The Art of Crochet and Knit Graffiti.” Authors Mandy Moore and Leanne Prain, of Vancouver, B.C., call yarn bombing “a quiet revolution,” a movement “that started underground and is now embraced by crochet and knitting artists of all ages.”

Last May, The New York Times published an article on yarn bombing with the headline “Graffiti’s Cozy, Feminine Side.” It was accompanied by a photograph of New York City’s “Charging Bull” statue, a symbol of Wall Street, encased in a crocheted purple and pink coat.

Prain, the Vancouver author, was quoted in The Times as saying she once tried to yarn bomb a signpost near FBI headquarters in Washington, D.C. The article said Prain was approached by a guard and told to “step away with the knitting.”

Walstad, who works in a clinic as an assistant, took her first foray into yarn bombing on June 11 — proclaimed on a Facebook page as “International Yarn Bombing Day.” She decorated the Colby Avenue pear statue that day. In October, during the Making Strides Against Breast Cancer fundraising walk in Everett, she scattered yarn flowers and yarn bosoms around town.

Suzanne Tidwell, of Sammamish, is a yarn bomber turned sanctioned artist. The 43-year-old’s interest began when she took a University of Washington certificate course in fiber arts.

“Getting your work out there, it’s hard to approach a gallery,” Tidwell said Wednesday. “The easiest thing to do is just put it up. For me, that’s how it started.”

Without permission, she wrapped a pole in yarn on a Redmond street, making it look like a candy cane. “I didn’t get in trouble. It stayed up for a year,” she said. “I ended up taking it down myself.”

Earlier this year, she saw a call for artists posted by Seattle Parks &Recreation for its summer ArtSparks program. Her proposal to wrap tree trunks and light posts in Pioneer Square’s Occidental Park was accepted. It took her a month to install the eye-catching display, which stayed up most of the summer.

“I’m rather a Girl Scout, I like to ask for permission,” said Tidwell, who has also wrapped tree trunks for the city of Sammamish. She believes yarn bombers spread a happy message: “Quit taking life so seriously.”

“I love the idea of people walking along and being taken aback by a fabulous array of color,” Tidwell said.

In Everett, holiday yarn bombers worked on a smaller scale, but with a similar message.

“It’s fun to spread joy, to bring a smile,” Cassie Smith said.

Julie Muhlstein: 425-339-3460, muhlstein@heraldnet.com.