BTS and Jimmy Fallon surprising fans is both adorable and hilarious

We know how passionate BTS stans can be, so imagine how fans react when unexpectedly confronted by the band themselves.

In the Tonight Show clip above, BTS fans are asked to go into a room to record themselves singing along to one of the band's new songs, SWIM. The twist? When they open the door to leave, they're greeted by the band themselves (plus Jimmy Fallon) waiting on the other side.

Bonus points for the random activities BTS and Fallon are up to when the fans come from the door...