Katy Perry says she made a 'big mistake' passing on collaboration with Billie Eilish

Katy Perry Reflects on ‘Huge’ Mistake of Passing on Opportunity to Work With Billie Eilish

Katy Perry Shared Why She Originally Declined Working With Billie Eilish — And How She Regrets It

Katy Perry Says She Passed On The Chance To Work With Billie Eilish: 'Huge Mistake'