Here's the themes for every couple. I've included every canon couple (even the ones that have broken up) and three one-sided crushes.
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TylerxLindsay: Hot sa pamamagitan ng Avril Lavigne

IzzyxOwen: Hot N' Cold sa pamamagitan ng Katy Perry

CodyxSierra (one-sided): Snow White reyna sa pamamagitan ng Evanescence (Most of the song is from Cody's point of view. The chorus is from Sierra's point of view.)

CodyxGwen (one-sided): High Above Me sa pamamagitan ng Tal Bachman

CourtneyxDuncan: I Hate Everything About You sa pamamagitan ng Three Days Grace

HaroldxLeShawna: White N' Nerdy sa pamamagitan ng Weird Al Yankovick

HaroldxHeather (one-sided): Just the Girl sa pamamagitan ng The Click Five

TrentxGwen: She Will Be Loved sa pamamagitan ng Maroon 5

BridgettexGeoff: Spaceship sa pamamagitan ng Puddle of Mudd (They DO make-out a lot...)

DuncanxGwen: The Rock ipakita sa pamamagitan ng Blink 182

HeatherxAlejandro: Evil pag-ibig from Phineas & Ferb -or- She Hates Me sa pamamagitan ng Puddle of Mudd -or- Womanizer sa pamamagitan ng Britney Spears (Yeah... this couple gets three, LOL. But they all fit so perfectly!)
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If you're confused about why I picked certain songs, just askk me and I'll say why. :)