ACLU benefit with art, music and film from 9 p.m. to midnight Friday (with doors at 8 p.m.) at the Massasoit Elks Lodge, 55 Bishop Allen Drive, Central Square. There is a $10 cash or credit card donation at the door, with all proceeds going to the ACLU.

The civil liberties-conscious parties roll on in these suddenly perilous times, this week featuring music – by Jack Romanov (who will be holding a debut screening of the band’s “Par for the Course” music video mini-series); Snowhaus; and Wendy Eisenberg – and art by Abby MacLeod; Sam Aprea; Emily Pardee; Quinn Viens; Natalia Klos; Ashley McDonald; Juan Esteban Cajigas; and by and from the traveling Feminist Fiber community. The show is 18-plus, but there’s a cash-only bar for those 21 and older. Information is here.

Free chocolate tasting from 1 to 2 p.m. Saturday on Brattle Plaza, Harvard Square (in front of Crema Café).

Part of Harvard Square’s 9th Annual Chocolate Festival, businesses including Cabot’s Candy, Crema Cafe, DavidsTeaEl Jefe’s Taqueria, En BocaFlour Bakery, Henrietta’s Table, Hotel Tria, J.P. Licks, Shake Shack, Starbucks, Toscano, Wagamama and Zinneken’s have contributed free samples to this popular and all-too-brief event. (Come early.) And stop by Capital One Café, 24 JFK St., for a free small chocolate drink between 1 and 3 p.m. Friday through Sunday. Information is here.

The 39th Annual Sci-Fi Marathon starting at 7 p.m. Saturday at the Massachusetts Institute of Technology’s Building 26-100, also known as the Compton Laboratories, at 60 Vassar St. Free.

The marathon – the 39th annual such event put on by the institute’s Lecture Series Committee – features four full-length films (“Edge of Tomorrow” at 7 p.m.; Oscar-nominee “Arrival” (above) at 9:15 p.m.; classic trash “It Came from Outer Space” at 11:45 p.m.; and “E.T. the Extra-Terrestrial” at 2:15 a.m.), one surprise feature at 1 a.m., many short subjects and refreshments. Pizza pre-orders will be taken between “Edge of Tomorrow” and “Arrival” for pickup before “It Came from Outer Space,” and breakfast foods will be available before “E.T.” Information is here.

Tchaikovsky’s “Eugene Onegin” by the Boston Youth Symphony Orchestras from 3 to 6 p.m. Sunday at Sanders Theatre, 45 Quincy St., near Harvard Square. Tickets are $35 to $50; everyone must be seated before 3 p.m. (or wait more than an hour until after Act I).

More than than 100 young musicians from the Boston Youth Symphony Orchestras are taking part in this one-time event bringing to life a dark tale of drama, selfishness and rejection – an opera in three acts based on the eponymous novel by Alexander Pushkin. (The opera retains much of Pushkin’s words, but adds texts by Tchaikovsky.) This semi-staged production will be sung in Russian with English supertitles. Among the young musicians performing Sunday are Cantabrigians Mai Nguyen, 15, and Ina Suresh, 17, both flutists; and Sun-Jung Yum, 15, playing viola. Longtime Cantabrigian Catherine Weiskel is the orchestra’s executive director. Information is here.

1Fest hardcore music event from 5:30 p.m. to midnight Sunday (doors are at 4:30 p.m.) at the “Hardcore Stadium,” also known as the Massasoit Elks Lodge, 55 Bishop Allen Drive, Central Square. Tickets are $10 (or $11.50 with the online service fee) or $15 at the door.

Descending on Cambridge from dates in New York like a bat out of … well, New York are this festival and its ear-blasting dozen bands: Siege; ACxDC; Cloud Rat; Die Choking; Escuela; Goolagoon (above); Grindmother; Cinderblock; Ascend/Descend; Suffer on Acid; Lunglust; and D-Sagawa. Information is here.