Last night's season finale of 'SNL' marked Fred Armisen's last episode as a cast member, our sister site ScreenCrush reports, and to mark the occasion, he performed a goodbye song as Ian Rubbish, the Margaret Thatcher-loving British punk character he debuted earlier this season. But that's not all: Midway through the tune -- a jaunty number called 'It's Gonna Be a Lovely Day' -- Armisen was joined onstage by his 'Portlandia' costar, former Sleater-Kinney singer Carrie Brownstein, the first in a string of guest rockers that included Dinosaur Jr.'s J. Mascis, Kim Gordon of Sonic Youth, Steve Jones of the Sex Pistols, Aimee Mann and Michael Penn. Watch it above.

Armisen, of course, is no stranger to punk rock, and before coming to 'SNL,' he played drums in the band Trenchmouth. “It’s been all right / I’ve had a lovely night with you," Armisen sang during the star-studded performance, successfully copping a Cockney accent and saying farewell in a way that was smart, funny, heartfelt and in no way sappy. Cheers, mate!