Taylor Swift and Sam Smith are total BFFs - thanks to Ariana Grande!

Although the pair had performed together on stage, it wasn't until they were seated next to each other at the 2014 American Music Awards in November that they REALLY hit it off.

TayTay and Sam were spotted dancing and cheering when Ariana was performing, and their mutual appreciation for her butt-shimmyingly sexy set sealed the deal on their friendship.

"We were front row watching Ariana Grande, loving her performance," Taylor told Rolling Stone. "We're both pretty animated when we're watching other artists. At the end of her performance, she did some dance move that was so sexy and so cool, and at the same time, Sam and I both screamed out 'YAS BITCH YAS!!' and then looked at each other and died laughing. I had this feeling that we'll be friends for life."

And she was right - the next week Sam was one of many people at Tay's 25th birthday party in her New York City apartment. Who knew Ariana Grande's butt was so powerful???