BTS dished on the most "amazing" parts of making "Butter," their latest Billboard Hot 100 No. 1 hit, in a new Facebook interview Friday (June 4). The K-pop boy band's second English-language single had a smooth start to the top of not just the Hot 100, but also the Billboard Global 200 and the Billboard Global Excl. U.S. tallies in the June 5-dated week. But the line that most members have stuck in their heads was sung by the one and only Jung Kook at the very beginning of the song.