Katy Perry may be one the biggest female music stars out there, but she's always got time to help out a pop sister.
Her 2008 album One Of The Boys saw her switch from Christian rock warbler to shiny superstar full sassiness and spectacle, but it also opened her up to songwriting for other big names in music. And as you'll notice from all the songs below, K-Pez has only showed interest in helping out her female peers so far.
Here are eight big pop tracks that you probably didn't realise Pezza helped write.
1. KELLY CLARKSON: 'I DO NOT HOOK UP'
Katy Perry originally wrote this song for an unreleased album between her self-titled debut Katy Hudson and her breakthrough record One Of The Boys, but after she pegged it from her former label Def Jam, she decided to give this power-pop anthem to Kelly Clarkson. Of course, Clarko gave it some extra oomph with her almighty vocals and turned it into a storming rock-pop ode to all the classy girls out there *insert nail polish emoji*.
2. BRITNEY SPEARS: 'PASSENGER'
While Britney's most personal album, Britney Jean, was a chart disappointment, Katy Perry actually helped co-write one the record's standout tracks. 'Passenger' is a soaring mid-tempo affair bigger than the all-star team behind it, which also includes Sia and Diplo. It really should've received single treatment.
3. SELENA GOMEZ: 'ROCK GOD'
Back when Selena Gomez was teamed up with her band The Scene, Katy Perry fered 'Rock God' as a cut for their second studio album A Year Without Rain. It sure has the same pop stomp that K-Pez made her name on with One Of The Boys. In fact, this is actually a secret duet really, as Katy can be heard singing with Selena on the actual finished track. Wonder what Selena's BFF Taylor Swift thinks about that now...
4. IGGY AZALEA ft. RITA ORA: 'BLACK WIDOW'
This is easily the biggest hit Katy Perry helped co-write without taking it to the upper echelons the chart herself. While the verses all belong to Iggy Iggs, Pezza is responsible for the earworm chorus sung by Rita Ora here. It's somewhat a cousin to her own trap-pop hit 'Dark Horse'.