1. John Legend wrote "American Boy"
I knew this track was iconic but I had no idea it was co-written by John Legend...and also will.i.am.
2. Pharrell Williams wrote "Hot In Herre"
I lowkey forgot all about Nelly and his bandaid, but I'll never forget this iconic tune.
3. Bebe Rexha wrote "Monster"
She co-wrote the 2013 song with Eminem and Rihanna, a year before releasing any of her own music.
4. Sia wrote "Diamonds"
Sia's actually written and co-written a ton of iconic pop songs, like Camila Cabello's "Crying in the Club", Britney Spears' "Perfume", Beyoncé's "Pretty Hurts" and Katy Perry's "Chained To The Rhythm".
5. Jessie J wrote "Party In The USA"
Jessie was originally going to record it, but it was decided that it wasn't "edgy" enough for her. IDK how a Brit was going to sing about Nashville parties but oh well.
6. Katy Perry wrote "I Do Not Hook Up"
Katy originally wrote it for her own album, but ended up giving it to Kelly Clarkson when she switched record labels.
7. Bruno Mars wrote "Forget You"
And remember when Gwyneth Paltrow sang it on Glee? A true pop culture moment.
8. Kesha wrote "Till The World Ends"
She said about the track: "I’ve never been more proud of anything in my career... It really solidifies me as a songwriter in the pop music world, which is what I consider myself first and foremost."
9. Ne-Yo wrote "Irreplaceable"
It was originally written as a country song, which is something I really need to hear.
10. P!nk wrote "Whataya Want From Me"
P!nk wrote it with Max Martin and Shellback for her Funhouse album, but it didn't make the cut.
11. Avril Lavigne wrote "Breakaway"
It was intended for Avril's album Let Go but didn't quite fit the vibe, so Kelly Clarkson recorded it for the Princess Diaries 2 soundtrack.
12. Christina Milian wrote "Baby"
Man, whatever happened to Christina Milian?
13. Prince wrote "Nothing Compares 2U"
It actually featured on an album from Prince's side project band, The Family, in 1985.
14. Jay-Z wrote Bugs Bunny's rap, "Buggin'" from Space Jam
15. Pharrell Williams wrote "Milkshake"
And it was originally offered to Britney Spears for her In The Zone album.
16. Ed Sheeran wrote "Strip That Down"
I love the idea of Ed Sheeran sitting down and writing "I used to be in 1D, now I'm free". Ed's also written a bunch of other huge pop songs, like Bieber's "Love Yourself", 1D's "Little Things" and Major Lazer's "Cold Water".