The singer took to the stage at a karaoke bar on Catalina Island, California on Monday night, where she attempted to rap Will Smith's 1998 hit 'Welcome to Miami'.
And yes, "attempt" is the right word.
After stumbling through the song's opening line, Katy left most of the hard work to her co-star friend while taking on the role of back-up singer.
Not surprisingly, the27-year-old's performance didn't provoke the kind of uproar she's used to.
You'd think Katy would have learned her lesson by now: after all, this isn't the first time she's tried her hand at rapping. In March this year the singer was slammed by fans after attempting to perform Jay-Z and Kanye West's song 'N----s in Paris' at a BBC Radio 1 concert.
Check out the clip above, and see our 'Celebrities who try to rap' slideshow for more cringe-tastic moments!