8 Big Pop Songs You Didn't Know Were Written by Katy Perry

Katy Perry may be one of 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 of 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, Perry has only showed interest in helping out her female peers so far.

Here are eight big pop tracks that you probably didn't realize Perry 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, Clarkson 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.

2. BRITNEY SPEARS: 'PASSENGER'

While Britney's most personal album, Britney Jean, was a chart disappointment, Katy Perry actually helped co-write one of 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 offered 'Rock God' as a cut for their second studio album A Year Without Rain. It sure has the same pop stomp that Katy 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 of the chart herself. While the verses all belong to Iggy, Perry is responsible for the earworm chorus sung by Rita Ora here. It's somewhat of a cousin to her own trap-pop hit 'Dark Horse.'

5. ASHLEY TISDALE: 'TIME'S UP'

When Ashley Tisdale was still trying to scrub that Sharpay sheen away, Katy Perry came to her aid with this scuzzy pop-rock number. Okay, so 'Time's Up' was only a bonus track on the iTunes version of the album (jeez), but it has all the hallmarks of a Katy Perry bop; a hands-in-the-air chorus, defiant break-up lyrics and spot of fierce attitude.

6. NICKI MINAJ ft. ARIANA GRANDE: 'GET ON YOUR KNEES'

While we all still wait for Nicki Minaj and Katy Perry to come together on a record, the closest we have so far is 'Get On Your Knees.' The singer-songwriter is actually responsible for the hook sang by Ariana Grande. Though, if you listen carefully, Minaj does actually give Perry a shoutout on the track.

7. SELENA GOMEZ: 'THAT'S MORE LIKE IT'

After giving Selena 'Rock God,' Katy Perry offered her another track for her final album with The Scene. 'That's More Like It' featured on 2011's When The Sun Goes Down and is a thumping pop affair with jittery video game electronics. The overall production of the song feels a bit scattered, so we're not really surprised Perry off-loaded this one really.

8. KELLY CLARKSON: 'LONGSHOT'

While 'I Do Not Hook Up' received single treatment, Katy Perry also gave Kelly Clarkson 'Longshot' for her 2009 album All I Ever Wanted. It's yet another example of Perry's affinity for guitar-bolstered pop anthems, with a chorus designed to lose your voice to.

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