Watch: Courtney Barnett's 'Nobody Really Cares if You Don't Go to the Party'

The signs began popping up around the globe. Giant, teasing signs in London, New York, Los Angeles, Melbourne, and Sydney. That inevitably led to people shooting selfies and sharing on social media.

Then last week, Australian indie rocker Courtney Barnett -- which Out called 'the new bard of rock,' hailing her debut album, Sometimes I Sit and Think, and Sometimes I Just Sit, 'as self-assured a debut as you could wish for -- performed a guerilla set for the new single, "Nobody Really Cares If You Don't Go to the Party," during an unannounced live set outside Camden Town tube station in the heart of London.

Check out the rest of her tour dates here.