Katharine McPhee Shakes Her Booty at Jason Derulo on ‘Lip Sync Battle’ (Video)

The “American Idol” runner-up throws off her good girl image to swing on a stripper pole to one of Derulo’s own hit songs

Last Updated: April 8, 2016 @ 3:39 PM

As “American Idol” bid farewell to fans with its final episode on Fox, the show’s Season 5 runner-up Katharine McPhee danced her ass off over on Spike.

The “Scorpion” star took on Jason Derulo on the hit fake-singing competition show “Lip Sync Battle” and proved she wasn’t a sweet and innocent girl next door anymore.

McPhee turned the heat up out of the gate with a booty-jiggling rendition of “Shake It Fast” by rapper Mystikal, which clearly impressed host LL Cool J.

However, it was Derulo’s bare-chested performance of “Pony” by Ginuwine that made Chrissy Teigen want to jump into his saddle and ride him.

McPhee responded by channeling her inner stripper — swinging on a pole in a satin bustier and getting thrown onto a fur-coat-strewn bed by a ripped male dancer, ironically to the tune of one of Derulo’s own hits, “Want to Want Me.”

“It’s a whole new Katharine tonight,” LL Cool J marveled.

Derulo counter-attacked by getting transforming into “Super Freak” singer Rick James, complete with sparkly spandex and plenty of hip thrusts in tight leather pants.

After a night of raunchy performances, the audience had the tough job of picking a winner — which was ultimately McPhee.

“I never win, ever — I was on a show that I lost,” she said, referring to “Idol,” adding: “I finally won something!”

“Lip Sync Battle” airs on Thursdays at 10 p.m. on Spike.