'American Idol': Katy Perry on Why She Went All Out for Disney Night With Ursula Transformation (Exclusive)

The 'Idol' judges opened up to ET after Sunday's live show and dished on Perry's jaw-dropping 'Little Mermaid' ensemble.

American Idol turned to the iconic soundtracks of beloved Disney classics for their new live episode on Sunday, and judge Katy Perry embraced the theme of the night by cosplaying as one of the most iconic Disney villains of all time: Ursula the sea witch.

Rocking the baddie's iconic tower of white hair and painting her skin purple, Perry was picture perfect as the evil witch from The Little Mermaid -- but amazing hair and make-up weren't enough for her.

The pop superstar -- who famously puts a lot of effort into her bombastic fashion choices -- decided to pull out all the stops for her costume and added on some black and purple tentacles to her incredible sequined ensemble.

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As the star sat alongside judges Luke Bryan and Lionel Richie, Perry evoked her iconic character all night -- from the way she chowed down on seafood at the table to the way she teased her co-stars with her fishing-line-controlled tentacles.

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ET spoke with Perry and her fellow judges after the show on Sunday, and the 34-year-old songstress opened up about why she chose to dress up as the beloved antagonist in honor of Disney night.

"I was thinking about [being] the Little Mermaid but then I realized, Ursula is a character who isn't done very much, [while] the Little Mermaid always gets her moment in the sun!" Perry explained, in the character's menacing tone. "And Ursula, actually, really wants Ariel's voice. And that's what I want, is these contestants' voices!"

Bryan, who donned his regular duds for the occasion, admitted that he was impressed by Perry's dedication before he ever even saw her outfit.

"She's the queen of shock factor," Bryan told ET as he stood next to his tentacled co-star. "I was in my trailer, looking like me, and somebody goes, 'Katy is gonna be Ursula.' And I go, 'Is she purple all over?' And they said, 'She's purple all over.' I went, 'God, I love that woman. I love her.'"

While Perry was only playing the villain on Sunday, all three judges were forced to bite the bullet and say goodbye to two singers in the Top 10 by refusing to use their limited save ability.

After all the songs were sung and America's votes were counted -- for the first public vote this season -- the two contestants who found themselves on the chopping block were Dimitrius Graham and Uche, who had both had been saved from elimination by the judges last week.

Uche, who failed to wow the judges with his rendition of "I2I" from A Goofy Movie, and Graham -- who actually delivered one of the night's top performances with a cover of "You’ll Be in My Heart" from Tarzan, that apparently just failed to connect with voters -- were eventually sent home after the judges declined to save them.

"We have to narrow it down, sooner or later," Richie told ET after the episode. "And America's voting now, so we have to kind of listen."

"We're limited on when we can pull that trigger," Bryan added, referring to the fact that the judges can only use their save option one time during the live voting rounds. "[And] those guys were in jeopardy last week."

Meanwhile, Laci Kaye Booth, Wade Cota, Alyssa Raghu, Jeremiah Lloyd Harmon,  Laine Hardy, Madison VanDenburg, Alejandro Aranda and Walker Burroughs got the votes needed to move them on to the season's Top 8.

American Idol airs live, coast to coast, at 8 p.m. ET, 5 p.m. PT on ABC.