Saturday afternoon's 11th annual What the Fluff festival brought out local restaurants, residents and fluff enthusiasts for a day of marshmallow-inspired fun in Somerville's Union Square. The yearly event celebrates the invention of Marshmallow Fluff, the sticky, sweet spread invented by Somerville's Archibald Query in 1917. Guests were invited to participate in Fluff-inspired games, while noshing on Fluff-coated treats and watching Fluff-twinged entertainment.