Gotye, Opera in the Outfield, DC Green Festival and the 18 best things to do in D.C. this weekend Gotye performs at Merriweather Post Pavilion this weekend. (Carlo Allegri/Reuters) It was one of the songs that fought mightily to stay planted in your ear (In truth, we all know "Call Me Maybe" won out). "Somebody That I Used to Know" propelled its author and performer, Gotye, from unknown Australian singer to mega-star. Case in point: In our area, he went from playing the 9:30 Club to Merriweather Post Pavilion, which is where he'll be this weekend.Along with 2012"s favorite kiss-off, Gotye is sure to play "Easy Way Out," "Bronte" and other cuts from his YouTube gold mine. The show is one of the items our list of the 21 best things to do in the D.C. area this weekend. Also featured: On Saturday, the outfield normally patrolled by Jayson Werth and Bryce Harper will be overrun by lawn chairs, picnic blankets and opera lovers. For Opera in the Outfield, the big center field scoreboard will show a live stream of the Washington National Opera performing Mozart's melodrama "Don Giovanni." Gates open at 5 p.m. for pre-show activities and entertainment, including stage-fighting demonstrations and flamenco dancing. If you've ever wanted to go green, you can spend this weekend at the DC Green Festival, which features DIY demonstrations, a green film festival, speakers, workshops and a marketplace, all under one roof.