Jam’s for s(m)uckers.

In Somerville, lip-smacking marshmallow Fluff reigns supreme in sandwiches, and there's a festival to declare it. The What The Fluff? festival returns this Sunday, Sept. 24 to honor the city’s legendary + creamy sandwich spread, which was concocted by confectioner Archibald Query in the early 20th century.

For year No. 18, the festival will occupy a stretch of Somerville Avenue between Dane Street and Warren Avenue, swirling Fluff-themed fun in Union Square from 3 to 7 p.m.

Here’s the rundown of the afternoon.

Getting there

The MBTA will offer shuttle service to Union Square, due to the current service suspension between Lechmere and the Union Square Station.
Three shuttles will run between the East Somerville Station and Union Square Station from 2:30 p.m. to 7:30 p.m.
The Route 87 bus can make connections to Somerville Avenue at Stone and Loring Avenues.
Bike valets will also be available on Somerville Avenue at the corners of School Street and Warren Avenue, courtesy of MassBike.

Sticky shenanigans

Indulge in Somerville’s invention from a distance by checking out live entertainment on the Fluff’n Jam Stage, featuring music from local artists like Grace Givertz + The White Owls. Adventurous guests can get their hands dirty at the aptly-titled Shenanigans Stage, which will bring a sticky twist to musical chairs, jousting, and limbo. Review the full schedule.

Can’t-miss treats

Find these experimental takes on Fluff favorites throughout the festival.

Oysters FLUFFefeller — Bluefin
Fluffernutter donut — Union Square Donuts
Canned Fluff cocktails — Nook Somerville
Orange Creamsicle Cocktail topped with Fluff — Saus at Bow Market
Fluff Naan and Fluff Samosas — Masala Square Indian Kitchen

UPDATE: This article now reflects the festival's rain date, Sunday, Sept. 24.