The Boom Clap hitmaker was invited to Perry's Los Angeles mansion for the first time for a daytime gathering last summer (14) and she chose to go straight there from a boozy night out, but ended up slumped next to the star's toilet.
She tells Britain's Fabulous magazine, "I passed out in her toilet... I'd been out the night before because we'd finished a video shoot and I rolled straight to this barbecue and it was a bit of a nightmare. I had one drink and was like: 'Oh God, game over!'"
Asked if Perry found her in that state, the singer replies, "No, thank God, but she did say to me: 'You looked really terrible earlier'. I was like: 'Thanks. You can count on me, Katy'. It's fair to say I made a great, solid impression."