Somerville’s annual “What the Fluff?” Festival returned to Union Square on Saturday, September 19. This year’s theme, “Legally Fluff: A Toast to Union Square,” celebrated the festival’s 21st year. Community members of all ages enjoyed free festivities honoring the invention of Marshmallow Fluff and the neighborhood’s creative spirit. The festival honors the invention of Marshmallow Fluff by Archibald Query in Somerville in 1917 and salutes the spirit of innovation that still thrives in Union Square today.  ~ Photos by Matthias Gat