The ladies joined L.A. Reid and Simon Cowell at the judges' table for two rounds of auditions on Thursday in Austin, Texas.
So, how were the contestants?
"Texas has a lot of talent - seriously! Loving @TheXFactorUSA auditions so far," Spears Tweeted Thursday.
She also took to Twitter to address some online reports that she walked off the set after someone who was auditioning offered a less-than-stellar rendition of her hit "Hold It Against Me."
The singer Tweeted: "#Britneywalksoff??? LOL was just taking a little break people. I am having the BEST time!!!"
And a source close to the show tells PEOPLE, "She was not upset. She just took a short break, which is not uncommon for judges to do in these taped shows."
Another source on the production clarified Spears's brief absence, telling PEOPLE, "The judges are allowed to get up at any point. The show isn't so strictly structered as [American] Idol is. When Britney got up, she went to fix a small wardrobe issue and had a bathroom break."
For her part, Lovato was equally impressed with the performers: "Such an amazing day...can't wait to do it again!!! #XfactorUSA," she Tweeted.
And Lovato and Spears got interactive, according to the source, who says, "[Britney] had a great time and even danced with Demi during one contestant's performance."
One of the best audition days we have ever done. @TheXFactorUSA— Simon Cowell (@SimonCowell) May 25, 2012
Courtesy The X Factor
Reporting by Jennifer Garcia and Marisa Laudadio