Credit: Ray Mickshaw/FOX ©2013 Fox Broadcasting Co.

There’s nothing toxic about Alex & Sierra.

The dynamic duo performed the Britney Spears’s pop classic for their X Factor audition and despite the song’s poison-laced lyrics, Alex and Sierra’s natural ease around one another completely won over the judges. “You’re really in love, aren’t you?” judge Simon Cowell said during their introduction. “You all are really cute,” Kelly Rowland chimed in.

Really cute and really talented. The pair, who are both 22 and have been dating for two years, blew the judges away with their first performance on The X Factor. “Not only are you talented, but you’re so down to earth ... I’m excited. I’m rooting for you. You’re so cute together. There’s magic,” Demi gushed. “It inspired me,” Paulina said. “I believe in you guys. I believe in love.”

In case you’re worried the dual demands of dating and performing together aren’t conducive to love, never fear.

“We do a lot of stuff together but, I mean, it’s no more than any other group that have to be together and practice,” Sierra says. “If anything, I think it’s better that we’re best friends and we’re dating.”

“Yeah, because we can be driving to a date and [be] practicing,” adds Alex. (They really do this, by the way: singing in the car to try out future songs worth performing.)

Credit: Ray Mickshaw/FOX ©2013 Fox Broadcasting Co.

Alex, who also plays the guitar, is no stranger to the stage but Sierra took a little more convincing. She would go to Alex’s gigs but says, “I always wanted to sing but I wasn’t as confident in my singing voice.” “But I’d beg her to come up and sing with me,” Alex explains. From those impromptu performances bloomed both a romance and musical partnership.

When they heard The X Factor was coming to town, it seemed like the perfect opportunity to test out their act on a larger stage.

“We both have really wanted to work with Simon Cowell,” Sierra says. “We always wanted to sing for him just because he is so honest. It’s kind of intimidating but, you know, if we’re not good, we wanted to hear from him that we weren’t good.”

Simon, of course, said quite the opposite in his critique both of their audition and their Four Chair Challenge performance (they sang Grease’s “You’re the One That I Want”). To make their X Factor experience even better, Simon is the mentor for Groups, news that got a memorable reaction from Alex.

“Alex is going to be so mad at me for saying this … he definitely teared up,” Sierra says when they heard Simon would be their mentor. “I’ve never heard him scream louder.”

“I didn’t scream,” Alex says. “I yelled.”

“Oh okay,” Sierra says. “Alex was facing the other way and I went to look at him and he was definitely, you’re eyes were definitely watery.”

“A little bit,” he admits.  “I was excited because that was best-case scenario.”

Beside wanting to perform for Simon, there was another draw to trying out for The X Factor. Unlike other reality music competitions, the show allows duets to audition together. Going it alone wasn’t an option, even if they’d been offered the chance to move ahead individually.

“We wouldn’t have moved on without each other,” Sierra says. “We’re a package deal.”

Elisabeth Kramer is an Assistant Editor at Wetpaint Entertainment and our resident Downton Abbey expert. Follow her on Twitter and Google+!