But now the girls are making the transition from online sensations to pop stars with their brand-new single, "Release You," which is available on iTunes.
The track, which has the makings for a summer anthem, is pure pop. With its sassy lyrics and an upbeat bouncy hook, "Release You" will likely be the go-to song for girls going through a breakup.
Megan and Liz Mace recently stopped by MTV News, and before playing a game of "Twintervention," where we had them guess other famous twins (check out the video!), they told us all about their new single.
"It's a happy upbeat breakup song, like, 'I'm gonna release you, bye, I don't care anymore,' " Megan said.
On the song, which is the lead single off their upcoming debut album, Look What You Started, due out late summer, the girls sing, "You used to make me laugh/ But now you make me sick/ Thought you were just so dope/ But now you're full of it."
"It's definitely girl power. We wrote it coming from real places," Liz said. "We are both kind of in that situation where, like, 'You know what? This just feels right,' and we are really, really excited about it."
The song, which was produced by Max Martin and Shellback with a co-write from Savan Kotecha, is reminiscent of some of Martin's biggest hits, with a message similar to Kelly Clarkson's "Since U Been Gone" and a catchy vibe like Taylor Swift's "We Are Never Ever Getting Back Together."
"It was definitely really intimidating at first when you walked in, because on paper he's just insane," Megan said of getting into the studio with Martin. "I mean, he's written so many songs, but once you get in there, all the fears and intimidations went away because he's so nice."