Lovato and Cowell were standing next to each other during the show's filming when Cowell turned to Lovato to ask the 20-year-old star a question, according to the Daily Mail. Lovato, startled by Cowell and with a mouthful of mints, took his hand to her mouth and spit the mints into his hand. If you're having trouble picturing what went down, try imagining a toddler handing its parent used gum -- only with less class.
"Really, really grown up, Demi," Cowell said, according to SugarScape. "You're an obnoxious little brat."
The Daily Mail reported that fellow "X Factor" judges Britney Spears and L.A. Reid couldn't believe what happened.
This incident follows the news that Lovato went on a date with Niall Horan of the pop group One Direction. The two have been flirting on Twitter for months, and there were reports Horan asked Lovato on a date when the two were at the MTV Video Music Awards show this week. There's even been speculation that a tweet by Miley Cyrus confirmed the relationship's existence.
Sugarscape reported that Lovato opened up to Cowell about what she and Horan have been up to. Although the report said Lovato doesn't have time for a relationship because of her role on "The X Factor," it's clear she's noticed Horan.
"Niall says hello," Lovato said to Cowell.
"Keep away from him. He's pure," Cowell dryly joked.
"I'm not going to date anybody for a whole year, and I made that clear to him," Lovato said through her laughter. You can watch a video of their conversation below.
Last week, Lovato appeared on "Live! With Kelly and Michael" and said she regretted getting her tattoos, accoutrements of the image that has made her famous. The star has an array of tattoos, but perhaps the most noticeable is the "Rock and Roll" artwork on her middle finger.
Lovato rose to fame with her roles in the "Camp Rock" films and the "Sonny with a Chance" television series -- both Disney productions -- before moving on to singing and now "The X Factor."
"The X Factor" makes its season premiere Sept. 12 at 8 p.m. EDT on Fox.