The "Boom Clap" singer recently joined Katy on the European leg of her Prismatic World Tour and, from the looks of it, Charli has been giving her Angels quite the performance.
"I'm going to do the biggest show that I have ever done," Charli told us on the Grammys red carpet, teasing her opening gig. "And Katy's been really cool. She's letting me bring a load of stuff, which is awesome, so it's going to be very in your face and very girl power."
This may be a preview of what's to come, too, since Charli told us she's planning her own worldwide tour in support of her album Sucker.
In the meantime, Charli, who recently released her single "Doing It" with Rita Ora, said she's working on a "couple of things" that she'd like to keep "a little secret."
Does that mean a Charli and Katy collaboration could be in the works? Fingers crossed.