What the Fluff? Marshmallow Festival from 3 to 7 p.m. in Union Square Plaza, 90 Union Square, Somerville. Free.

Delicious and horrible Marshmallow Fluff was invented in Somerville in 1917, when a local named Archibald Query invented it in his kitchen and sold it door to door. The city’s annual Fluff Festival honors the concoction in every way imaginable, including music and burlesque, a cooking contest (for which judges include Mari Levine, a senior editor at America’s Test Kitchen, and NASA astronaut Suni Williams), games such as Fluff Lick-Off, Blind Man’s Fluff and the Fluffernutter Relay and, of course, lots of Fluff-related foods, only starting with the classic Fluffernutter. There are 11 providers of Fluff-based sweets (including the offensively tasty and popular FluffaNutta Donuts from Union Square Donuts) and six providing savory foods.

A wrinkle for this ninth annual celebration: It’s steampunk-inspired, for a hybrid event organizers are calling Steamfluff, which at the very least brings a whole new range of vendors to the square. More information is here.

The Fifth Annual New England Americana Festival starting at noon Saturday. On Brattle Street in Harvard Square. Free.

New England Americana closes Brattle Street to traffic and replaces it with multiple stages with acclaimed local bands, a beer garden, vendors and artisans, family-friendly games and fun. Bands include Tigerman Woah!, Tallahassee, Dennis Brennan, Old Jack, Rick Berlin and the Nickel & Dime Band, Patrick Coman, Susan Cattaneo, The Blue Ribbons and more. (Even more bands are at the Friday evening Kick-Off Bash and 7 p.m. Saturday Wrap Party hosted at Passim, 47 Palmer St., Harvard Square. Each are $15 for the general public, or $13 for Passim members.) Information is here.

Bull McCabe’s Roots to Reggae Outdoor Music Fest from 2 to 11 p.m. Saturday at Bull McCabe’s, 366 Somerville Ave., Union Square, Somerville. Tickets are $15 (with a $1.82 service fee online).

If you live in Cambridge or Somerville and somehow aren’t into Americana, maybe a broader range of music will work for you? This third annual outdoor music family-friendly festival has outdoor dancing, eating, drinking and dancing to the sounds of Christian McNeill & Sea Monsters; The Johnny Come Latelies; Dub Down; Dub Apocalypse; Skiffy & the Ghetto People Band; The Nephrok Allstars – possibly some of the best dub and island music you’ll find at a traditional Irish Pub that happens to serve everything from hummus to nachos and buffalo tempeh.

“Back to the Future” at 7 and 10 p.m. Saturday at the Massachusetts Institute of Technology’s Building 26-100, also known as the Compton Laboratories, at 60 Vassar St. Free.

Who doesn’t love this movie? Marty McFly has to travel back to 1955 with scientist Doc Brown in a DeLorean time machine, meet his parents and literally race time to make sure his parents fall in love – incidentally inventing rock ’n’ roll and reminding us that we’re way behind on putting the hoverboard into production. This charmer has an 86 percent score on Metacritic and a 96 percent fresh score on Rotten Tomatoes. Even better, your admission and popcorn is free courtesy of the de Florez Fund for Humor at MIT. Information is here.

Lori McKenna CD release concert at 7:30 p.m. Saturday at The First Parish Church, 3 Church St., Harvard Square. Tickets are $25 to $30, or $23 to $28 for Passim members.

Stoughton native Lori McKenna marks the release of her acoustic record, “Numbered Doors” in a Passim-sponsored show.  The idea for this eighth album and its songs developed while on tour, staying in motels between shows, McKenna said. “Motel rooms were made for songwriting,” she said. “Think of all the stories that started or ended in that room. Think of all the feelings given into and the ones ignored. All the gossip that room could spit out about all the strangers that have come through. Ourselves included. The love made, the promises, the lies, the turning points and last hopes, the prayers.” Heather Maloney opens. Information is here.

Third Annual Festival of Dumplings from noon to 3 p.m. Sunday in Central Square.

This third annual festival in honor of local cooking legend Joyce Chen (and her U.S. post stamp, unveiled this weekend) means $1 dumplings throughout the square from restaurants including 1369 Coffee House (757 Massachusetts Ave.); The Asgard (350 Massachusetts Ave.); Dosa Factory (571 Massachusetts Ave.); The Middle East (472 Massachusetts Ave.); Patty Chen’s Dumpling Room (907 Main St.); Thelonious Monkfish (524 Massachusetts Ave.); Yoki (485 Massachusetts Ave.); and Zuzu’s (474 Massachusetts Ave.). Information is here.