PTX DROP NEW CLIP, HIT FALLON (AND BLOW UP iTUNES AND TWITTER)

With their new RCA album now out and #2 at iTunes, check out a cappella quintet Pentatonix in their new video for "Sing" and performing single "Can't Sleep Love" on Thursday night's Fallon. The vocal wonders also sang Fallon's opening theme, which is also below. The host was clearly stunned by their abilities, and so were Twitter followers; the episode became the second most Tweeted-about of the season, behind only the premiere.