When I was a kid, my mom often accused me of being a pack rat. I am mortified to confess that not only have I proven her right, I’ve proven her guilty of grossly underestimating me.

I blame Yellowball.

It’s an innocuous rubber playground ball that takes up very little physical space, but looms large over my conscience. Yellowball has been sitting in my office for three months — long enough to accumulate as much dust as the PROMO 100 files beside it.

Dust goes against the very essence of Yellowball, which was designed (by the Centers for Disease Control and its promotion agency, Arc Worldwide) to keep moving. Kids who get a Yellowball register its code at VerbNow.com, record what they did with the ball, then pass it on to another kid to play, report, and pass it on. By summer, there should be 50,000 Yellowballs traversing the world in one bouncy epidemic of juvenile exercise. And kids can use the code to track their own specific ball, where it goes and how other kids use it.

In theory, it captures my imagination.

In practice, I have flunked Yellowball.

I was pretty pumped when the ball first arrived. I pictured my kids frolicking in the yard, making up some game with a witty name, and then passing the ball on to — who? How could we get the ball far away, fast and make sure it kept moving? The cousins are all over the country, but who could we trust to really do something clever, and then hike our collective Yellowball into an exotic new ZIP code?

I chewed it over for weeks. I have friends in India. That would be cool. On the other hand, my college friend’s kids in Tennessee are about the right age for four-square-cum-computer. But then, my brother in Alaska is quirky; he’d do my Yellowball justice.

I, me, my. You’re starting to see the problem, aren’t you?

And here is my most shameful confession: My own kids don’t even know this ball is here. I’m afraid they’ll want to give it to their own friends, who live in our same ZIP code and play the same games and, well, we aren’t going to score very high in distance or creativity at VerbNow.com, now are we?

So I am a pack rat. But I am also a procrastinator and a control freak. Sorry, Mom.

I vow to give the ball to my kids right after dinner, while it’s sunny and 70 and I am pathetically guilt-ridden. As always, my kids redeem me. My daughter teaches me a four-square move called “Bubble” (throw the ball in the air and clap as many times as you can until you catch it). My son leads a game of “All Stars” (known in most circles as “Catch”), and when the neighborhood kids come over, we play “Gumball Machine” and some crazy combination of lacrosse, soccer and hockey where they all ended up just hitting each other in the shins with sticks.

Then, my son asks for help with his homework: Play with his new football and go online to register it. He writes out a code (Y6644) and a URL: www-dot-easterfootball-dot-org. We can’t find an Easterfootball.org Web site, of course, but when we google “Easter football” we discover a soccer camp in Lanarkshire, U.K.

One of these days, I’m sending our Yellowball over there.

Verb now has an adjective: Yellow. The Centers for Disease Control is going hand-to-hand viral for the latest phase of its Verb campaign that encourages kids to play. Like any good game, this one has lots of moving parts.

CDC is giving away 550,000 rubber playground balls and asking kids to play, then pass it on. Each Yellowball has a code on it; kids go to Verbnow.com to enter the code and blog about what they did with the ball before giving it away.

“We want to spread an epidemic of play among kids,” says Lori Asbury, marketing director at the CDC.

“There’s a cool responsibility when the ball lands in your hand to do something with it,” says Chris Cancilla, senior VP-group creative director at Arc Worldwide, lead agency on Verb. “You could sit on it or put it in your closet, but that would stop play from moving forward.”

Kids can use the code to track their ball’s journey and see how other kids have played with the same ball, and how far it travels from their hometown.

“They may know who they handed it off to, but to see how the ball is making its way across the country or in the community will keep kids engaged,” says Stella Kusner, Arc account director. (One ball has already gone nearly 40,000 miles, to Saipan and back.)

CDC watches the codes to track the action, too, so it can get more balls out there, or get balls in the marketplace moving more.

The CDC will give away 120,000 Yellowballs this spring through 6,000 middle schools. Gym teachers get 15 to 20 balls — half to dole out to their students, half to share with another local school — to jumpstart local sharing (and stretch CDC’s reach without adding distribution costs). A PSA airing in-school via Channel One supports.

Gym teachers answer seven questions about how they implemented the program, and kids’ response, to qualify for a grant of $500 to $2,000 via Kaleidoscope, the in-school marketing agency that’s distributing balls for CDC.

CDC will hand out another 150,000 balls over the summer through community groups such as the Boys & Girls Clubs of America, 4-H and the YMCA. Street teams will distribute 50,000 balls at parks, including skate parks, and another 50,000 at summer camps and festivals.

The first wave of balls went to kids who’ve opted into marketing programs, like Teen People’s Trendspotter brand ambassadors. (A contest tied to a Teen People ad buy awarded some balls as prizes.)

“When you’re selling physical activity, you want to make it tangible for kids. How can you experience physical activity in a fun, creative way?” Asbury says.

“The ball is the ball; it’s identical in every environment,” Cancilla says. “But the way it gets delivered is unique to specific environments. The fact that the idea is simple and pure lends it to extension. Play is a cause that kids can take up.”

Even virtual play. CDC teased Yellowball for three months, December through February, with playful displays in 110 malls and theater lobbies. Projected video displays from Reactrix respond to viewers’ movements: Kids interacted with yellow balls projected on the floor by virtually kicking, hitting and passing them. (The projector reacts to body heat and moves the balls when the kids move.) The displays also touted VerbNow.com.

The idea for Yellowball sprang from Verb’s current “Sun” TV spots created by Arc’s sister shop, Saatchi & Saatchi. Arc set the integrated marketing platform that Saatchi used to develop the TV campaign.

“A lot came together at once. A lot of the thinking that went into Yellowball was on a parallel path when Saatchi was working on the TV,” Cancilla says. “The ‘Sun’ ads are an over-the-top demonstration of Yellowball; we made it more tangible, something kids can get their hands on.”

Another inspiration came from Amsterdam’s bike-sharing system that lets members use one of the communal bright-yellow bikes whenever they want. (Toronto and Austin, TX have similar bike-sharing programs; Joensuu, Finland put out 200 yellow bikes for public use in the 1980s, prompting a rash of thefts. Many have been recovered.)

Yellowball is a departure from the online platform CDC used last year to launch Verb ViRTS, which lets tweens create an online character, then record hours of their own physical play to bank energy for their character. A search function lets kids find local activities by ZIP code. So far, kids have created 644,467 ViRTS; the program continues at VerbNow.com.

Arc coordinates Yellowball through a team of channel managers, who each handle one element: events, online, school/community tie-ins. Those channel managers work with Arc’s cross-functional creative team. Arc also coordinates with New York-based Saatchi and four ethnic marketing agencies: Garcia 360, San Antonio (Hispanic); PFI, New York (African-American); A Partnership, New York (Asian); and G&G Advertising, Billings, MT (native-American).

Having a simple central idea makes it easier to coordinate all the pieces. “That basic mechanic of making the ball desirable and making kids the spokespeople makes integration easier,” Cancilla says.

Plus, having one clear idea made it an easy sell-in at the CDC, Asbury adds: “We could see immediately how it works for Verb’s [mission] to bring play to kids’ lives in an easy way. We knew it was a winner of a concept.”