EXCLUSIVE: James Corden Reveals Katy Perry Was Deciding on 'American Idol' While They Filmed 'Carpool Karaoke'

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We might have James Corden to thank for Katy Perry's decision to join American Idol!

During an interview with ET's Leanne Aguilera at CBS Upfronts in New York City on Wednesday, Corden revealed that he and Perry discussed the offer while she was filming her upcoming Carpool Karaokesegment.

WATCH: It's Official! Katy Perry Will Be a Judge on 'American Idol' Reboot: 'I Want to Bring It Back to the Music'

"I talked to her about it, and on the day that we shotCarpool, she had to make up her mind that day," the Late Late Show host revealed. "She said, 'What do you think I should do?' and we talked it all out in the car."

"She also talked about a lot of things that she's never really talked about publicly before, so, yeah, it will be fun!" he added.

Perry's Carpool Karaoke segment will air on Monday as part of The Late Late Show Carpool Karaoke Primetime Special 2017, but before then, fans will be treated to a little Harry Styles.

WATCH: Katy Perry Spotted Singing 'Dark Horse' With James Corden While Filming 'Carpool Karaoke' in L.A.

"We have a big sketch tonight, and he performs another song," Corden teased of Styles' Late Late Show residency. "And tomorrow night we'll have Carpool Karaoke with Mr. Styles himself." 

"It's a really good one. It's the first one we'll have done this year... so we have that Thursday, Katy Perry Monday [and] Ed Sheeran in two or three weeks," he said. "It's an exciting time!"

Styles teased his Carpool Karaoke appearance -- and hilariously dodged questions about Kendall Jenner -- on The Late Late Show on Monday. Watch below: