21st Annual What the Fluff? Festival

What the Fluff? A Tribute to Union Square Innovation, a far-out festival honoring the invention of Marshmallow Fluff, returns to Union Square in Somerville on Saturday, September 19 from 1-5pm (severe weather date Sunday, September 20). Come play, delight in your food, and raise a glass to Union Square as What the Fluff? turns 21! This year’s theme – Legally Fluff: A Toast to Union Square – celebrates 21 years of fluff-filled fun for all ages. 

Join in (friendly) Fluff-forward competition on the Shenanigan’s stage (Fluff musical chairs, jousting, hair-do contest, anyone?). Feel the beat and move your feet with performances on the Fluff ‘n Jam stage and pop-ups throughout the festival. Interact with innovative activities and Fluff-themed public art. Secure some sticky (and not-so-sticky) artisan souvenirs and satisfy your sweet tooth with over 100 vendors. Snag your official What the Fluff? merch including limited edition 2026 items showcasing this year’s original design by local artist Jen Gubicza. And so much more!

This year’s festival will also debut an updated and expanded event footprint to better accommodate increased attendance, improve pedestrian circulation, maintain emergency access, and enhance overall event safety and attendee experience.

Whether you prefer your Fluff paired with peanut butter, in a delectable dish, or as a piece of art or collectable to take home, Legally Fluff has something for all tastes. Put on the party hats, blow up the balloons, grab a bubbly bev, and celebrate Somerville’s signature sweet spread in style. Prost! Sláinte! ¡Salud! Here’s to Union Square!

What the Fluff? is brought to you by Union Square Main Streets, a 501(c)(3) economic empowerment nonprofit organization, with a mission to strengthen the dynamic neighborhood of businesses and people in Union Square in partnership with the Somerville Arts & Culture Department as part of the ArtsUnion initiative to enhance the cultural economic development of Union Square.