The Gin and Juice hitmaker contributed a guest verse to Perry's 2010 track, which topped the singles charts in both the U.K. and U.S.
The I Kissed a Girl singer has now revealed she and her entire band became 'contact high' when the marijuana-loving rapper visited the studio and puffed on a joint during the recording.
Perry tells Britain's The Sun newspaper, "It was really cool. He came by the studio, played the song and rolled a 'J' (joint). Everybody was contact high. But he was super-cool and he's been around forever. It's really amazing if you meet someone that's been around for 20 to 25 years and they're still cool, because sometimes they ain't."