Observe a Festivus of Comedy at 3, 7 and 9:30 p.m. Saturday at the Davis Square Theatre, 255 Elm St., Somerville.

This series of shows runs roughly in accordance with Festivus traditions gleaned from this Brighton comedy troupe’s favorite “Seinfeld” episode. The lineup starts with the Airing of Grievances at 3 p.m. including Liquid Fun (from Boston University), False Advertising (from Brandeis), Natick Improv, Improv Jones and a Kitsch In Sync Alumni show. This show is $10. Then comes the Feats of Strength at 7 p.m., with standup comedy by Ben Quick and improv from Dead Pony Party Improv and a Kitsch In Sync Main Show. This show is $15. Finally comes the Festivus Miracles at 9:30 p.m., featuring standup comedy, Awkward Compliment Improv and a second Kitsch In Sync Main Show. This show is $15.

Tickets can be bought online or for cash only at the door. (On a nice but less funny note, the troupe is collecting Toys for Tots and the Greater Boston Food Bank. Toys brought to the shows should be packaged and unwrapped.

Enjoy free or cheap entertainment courtesy of MIT starting at 4 p.m. Saturday and running through 9:30 p.m. Sunday. The Massachusetts Institute of Technology is feeling restless or especially charitable or something.

Film: The weekend of cultural riches starts with free showings of Tim Burton’s “The Nightmare Before Christmas” at 4 and 7 p.m. Saturday at the school’s Building 26-100, also known as the Compton Laboratories, at 60 Vassar St.

Theater: Gilbert & Sullivan’s “H.M.S. Pinafore” is performed from 8 to 10 p.m. Saturday and 2 to 4 p.m Sunday by the school’s Gilbert and Sullivan Players at the Sala de Puerto Rico in the Stratton Student Center, 84 Massachusetts Ave. Tickets are $15 for the general public, $10 for MIT community, students from other schools and seniors or $5 for MIT students.

Music: The MIT Concert Choir, directed by William Cutter, performs Verdi’s “Stabat Mater” and “Te Deum” and Beethoven’s Mass in C major, Opus 86, from 8 to 10 p.m. Saturday at Kresge Auditorium, 48 Massachusetts Ave., for $5 entry; the MIT Chamber Music Society performs from 3 to 4 p.m. and 5 to 7 p.m. Sunday in Killian Hall in the Hayden Library Building at 160 Memorial Drive in a free concert; John Harbison’s 75th Celebration Concert, called “Definitely Not Retiring,” celebrates the professor and conductor’s 75th with surprise guests, the music of Bach and premieres of some of his jazz songs with lyrics by MIT students, among other treats, from 7 to 9 p.m. Sunday in Kresge, for $5 general admission (or free in advance to MIT community); and “Techiya Celebrates Thanksgivichristmukkahween” a free a cappella concert that celebrates all the season’s holidays at once from 8 to 9:30 p.m. Sunday at the Massachusetts Institute of Technology’s Building 6-120, also known as Eastman Laboratories, at 182 Memorial Drive.

Dance: “DanceTroupe Presents… DTWERK!” has sold out all of its shows except the 5 to 8 p.m. Saturday “Fixation & Ridonk” show. The suggestion here is that science geniuses twerk too. If you get tickets, the performance is at the Little Kresge, 48 Massachusetts Ave., for $10.

Hear some toy-donation, feel-good hip-hop at the Kulturez Dynasty Toy Drive from 6 to 11 p.m. Saturday at the store, 36 JFK St., Harvard Square.

Bring a toy for donation and the store will give 30 percent off any item from its selection combining elements of skate, graffiti, DJ, hip-hop, reggae, rock, punk and other cultures. (There will also be a raffle for some store items.) While you shop there will performances by Mas D, Muna, Lotus B, Jose from YosoyInc., Demetrius Lyrical Biz Bizzell and DJ Nexus. Toys will be donated to the Marine Toys for Tots Foundation. (If you can’t go, donate whenever you can and get the store discount until Dec. 14.)

Get some buy-local gift shopping done. Check out Christ Church Cambridge’s Christmas Fair (with 28 vendors listed here) from 10 a.m. to 3 p.m. Saturday at Zero Garden Street (across from Cambridge Common); the Mudflat Studio Open Studio and Pottery Sale (with the work of 103 artists noted here) at 10 a.m. Sunday at 81 Broadway, Somerville; and The Davis Flea Holiday Vintage Market (tripled in size since last year but still specializing in reclaimed and repurposed goods, as described here) at 11 a.m. Sunday at The Center for Arts at the Armory, 191 Highland Ave., Somerville. If you can’t find it at these gift fairs, maybe you weren’t meant to give it.

Relive “Foxtrot” by Genesis, as performed by The Musical Box at 8 p.m. Sunday at The Sinclair, 52 Church St., Harvard Square.

This is basically what you’d see if you knew enough to go see Genesis perform in 1973. The Musical Box has mounted a reproduction of the original concert in painstaking detail to give people the illusion of being at the actual Genesis show in its early Peter Gabriel stage, when the art-rock band was coming into its own as a mix of music and theater. The visual reconstruction of the show was based on photos and slides of the original concerts, as well as articles from papers and magazines and information offered by people who either worked on or attended the original “Foxtrot” tour. The band has even been known to use vintage instruments to guarantee the same sound coming from the stage, and it assures that the audience will be “flawlessly transported back in time.”

Tickets are $35 in advance or $37 the day of the show. Doors open at 7 p.m.