One might very well ask “What the Fluff?’’ That’s the name of the annual fall festival held in Somerville’s Union Square to celebrate the wacky idea of one Archibald Query. In 1917, Query invented sticky, whiter-than-white creamed marshmallow Fluff at his home near Union Square, and for nearly a century it’s been a childhood (and, for some, longer) staple treat, as loaded with nostalgia as it is sugar — almost.

Now in its 11th year, the festival — commonly known as FluffFest — has grown to become a carnival held at the intersection of Prospect Street, Washington Street, and Somerville Avenue. There are games like Knucklebones, Fluff Musical Chairs, Blind Man’s Fluff, Fluff bowling, and Pin the F on the Fluff boy. This year’s event will be held Saturday from 3 to 7 p.m. with a rain date set for Sunday.

The brave can get a Fluff hair-do, and then there’s Fluff jousting, which goes against everything Mom ever told us about getting that sticky stuff all over everything.

There’s a live music stage featuring R&B and funk from The Neprok! Allstars, Booty Vortex, and Miss Fairchild. There’s comedy at the Shenanigans Stage, which is overseen by Somerville personality and Archibald Query impersonator Mike Katz. There’s a cooking contest, which invites Fluff fans to create culinary delights. You need to preregister for that, though.

Fluff stuff aside, as FluffFest celebrated 10 years last fall, it capped a decade of the reinvention of Union Square as a commercial and cultural hub. This year, the festival’s full title is “What the Fluff? A Tribute to Union Square Invention.’’

“The festival captures who we are, who we were, and who we’ve become again,’’ says Esther Hanig, executive director of Union Square Main Streets, the organization behind FluffFest. “We have the best farmer’s market; Union Square has incredible dining experiences — from Thai to Portuguese to Brazilian to Juliet. (Juliet landed on Bon Appetit’s Best New Restaurants list.) We have four music venues in walking distance of one another; we have Aeronaught Brewery, and Bantam Cider. It is a truly innovative, but collaborative scene, and FluffFest is a big part of that.’’

Union Square’s eateries, bars, and stores will play up the white sticky goo shtick with Fluff-inspired nibbles, including whoopee pies and Fluffernutters, which you can wash down with a Fluffatini. Yes, it’s a real Union Square thing, a specialty at PA’s Lounge, served to those in the know. Ask nicely.

Linda Clarke can be reached at soundz@me.com.