Here's the updated version of what I think all of the TDI character's theme songs are. Some people have two, though, because I couldn't decide which one was better.
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Ezekiel: घर द्वारा Daughtry -or- Canadian Idiot द्वारा Weird Al Yankovich

Eva: Everybody Down द्वारा Nonpoint

Noah: Vicarious द्वारा Tool (I think it could be about his slightly sadistic qualities)

Justin: Sexy Back द्वारा Justin Timberlake

Katie and Sadie: True Friend द्वारा Hannah Montana

Tyler: Radio द्वारा Jim Johnston

Izzy: Psycho द्वारा Puddle of Mudd

Cody: Sombody for Me द्वारा Nikelback

Beth: Hazard to Myself (Don't Let Me Get Me) द्वारा Pink

Courtney: Circus द्वारा Britney Spears

Harold: Pork and Beans द्वारा Weezer

Trent: Everybody's Fool द्वारा Evanescence

Bridgette: Pocketfull of Sunshine द्वारा Natasha Bettingfield

Lindsay: My Boobs Are Okay द्वारा Lene Alexandra (I was going to put "Barbie Girl" but everyone does that one)

DJ: Where is the प्यार द्वारा The Black Eyed Peas

Geoff: Fight for Your Right to Party द्वारा The Beastie Boys

LeShawna: Please Don't Stop the संगीत द्वारा Rihanna

Duncan: Animal I Have Become द्वारा Three Days Grace

Heather: Sexy, Naughty, Bitchy द्वारा Tata Young -or- Cruella DeVille द्वारा Selena Gomez

Gwen: Sweet Sacrifice द्वारा Evanescence

Owen: Fat द्वारा Weird Al Yankovick

Alejandro: Perfection द्वारा Cage9

Sierra: Taking Over Me द्वारा Evanescence

Chris: Money द्वारा I Fight Dragons

Chef: Stoned द्वारा Puddle of Mudd

Blaineley: Piece of Me द्वारा Britney Spears

Mr. Coconut: Dr. Coconut from Phineas & Ferb

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If आप don't understand any of them, I'll explain. Just ask. :)