His One Direction bandmates say Niall Horan gets the most girls, and it's easy to see why: He's incredibly charming! So much, in fact, that he won the hearts of five famous ladies at one time -- the gals of Fifth Harmony!

Horan and the 5H girls met up on 'X Factor' this week, where 1D delivered a flawless performance of 'Story of My Life.' The lovely ladies performed 'Better Together,' and they, too, were pretty perfect. And now they're Twitter BFFs!

Niall tweeted how much fun he had on set of 'X Factor,' which we thought might be slightly awkward since his former crush Demi Lovato is a judge! (They're still pals, but have lost touch since the days when they were spotted on dates and Skyping all the time. Bummer, he's so much cuter than Wilmer Valderrama!)

Both groups are 'X Factor' alumni, though obviously 1D were created in the U.K. original version of the series.

Horan and Fifth Harmony are stoked to be part of the 2013 American Music Awards as well, which air tomorrow (Nov. 24) live at 8PM ET on ABC. Get your popcorn ready -- and your dancing shoes!