1999 is such a huge party jam that we're fanging to hear it live already, even though it only came out last week.
We're sure Charli XCX will give Australian fans a taste of the song at her upcoming shows with Taylor Swift and also at her Pop2 show in Sydney, but stoked New York City fans at Troye Sivan's show managed to cop Charli XCX guesting on the track for the first time live.
Troye was playing the famous Radio City Music Hall last night and surprise surprise, Charli was present to help him out for the song right at the end. Seeing both of them take on the throwback song is a huge mood - they've got choreography down, energy pouring out of their veins and it's just a dizzying fun time.
Check out some fan-shot videos below.