The X Factor: Ellona Santiago Has an 'Outstanding Night'
11/28/2013 AT 09:55 AM EST
The most heated exchange took place following Lillie McCloud's soaring performance of "Summertime," which earned a standing ovation from all the judges except Cowell, who said it "wasn't raw enough."
"I just wish I had been mentoring you," he said. "I would have done so much better."
"Simon, shut up!" (a newly engaged?) and outraged Kelly Rowland snapped.
When host Mario Lopez asked Rowland how she felt about Simon's remarks, she icily replied, "I don't. I don't."
And the two weren't ready to share pumpkin pie by the end of the show, when all the contestants took part in a group number, where they sang "Cry Me A River" but worked to stand out individually.
"Duh, Simon," Rowland said about Restless Road. "If I was your mentor, I would have made sure you harmonized."
Even Paulina Rubio was miffed, after Cowell compared her Boys performer Josh Levi to a "singing, dancing fly" following his choreographed performance of "Treasure" by Bruno Mars.
"No! No! No!" Rubio shouted over Cowell, stealing his mic.
Although Cowell referred to his female counterparts as "the Witches of Eastwick," Rubio and Cowell at least shared a laugh after 17-year-old Ellona Santiago stole the night with her stunning performance of Jessie J's "Mamma Knows Best," just a week after Cowell called her a "dancing, singing puppet."
"You are more than a muppet," Rubio said.
"I didn't say muppet, I said puppet," Cowell laughed, before saying, "Ellona, that is what we call a game-changer. You may now have a chance now of winning this whole show."
On a night when the contestants gave special thanks to their loved ones, Santiago's tribute to her sister Julie Rose, who's battling stage 4 cancer, touched everyone, including Cowell.
"I want to send out my love to your sister," he said, addressing Julie Rose, who was in the audience to see her sister's standout performance.
Michael Bublé, who mentored the contestants' group performance, and judge Demi Lovato will perform on The X Factor's elimination show, airing Thursday on Fox at 8 p.m.