I like how people say that "Cali Gurls" copied "Tik Tok," as if the latter is some original composition. When I first heard "Tik Tok," I thought of "Just Dance," particularly on the chorus.

Irreplaceable -- Tattoo -- Not Afraid -- New Shoes -- Disappear...

Some many others thrive on that same hi-hat pattern, and similar piano riffs and chord progression.

What ???

They actually do have a similar theme; waking up drunk, dancing, and getting even more drunk.

The California Gurls/Tik Tok debacle is pretty much a given.

Music Sounds Better Than You -- Get Together -- Trouble -- Tik Tok -- Calfornia Gurls

One does not wake up drunk, its called a hangover

Tohmahto.

They were crafted by Max and Dr. Luke; both of whom are pretty shameless.

when I heard Tik Tok and California Gurls, I thought about Love At First Sight of Kylie :-/

The Tedder songs (Halo and Already Gone) aren't either of the artists' fault, it's his fault; they both got basically the same track and neither of their albums were out yet when the songs were recorded. That's why Kelly was so pissed, because Halo being a single made it look like she jacked it from Beyonce.

Te Amo/Letting Go (Dutty Love) and Firework/Only Girl

Revolver sounds like a low-rent Radar.

Before i discovered Evermore, i thought Clocks - Coldplay & It's Too Late - Evermore sounds alike

Rihanna jacking Kelly Rowland? x100

Some of these have probably already been said, but...

Metro Station - Shake It
Runner Runner - So Obvious

P!nk - So What
Ashley Tisdale - It's Alright, It's OK

Katy Perry - Hot N Cold
Ashley Tisdale - Erase and Rewind

Ace of Base - Don't Turn Around
Lady GaGa - Alejandro

Britney Spears - If U Seek Amy
Miley Cyrus - Can't Be Tamed

Britney Spears - Radar (intro only)
Christina Aguilera - Keeps Gettin' Better
Kaci Battaglia - Crazy Possessive

Beyonce - Irreplaceable
Rihanna - Take a Bow
Jordin Sparks - Tattoo
David Archuleta - Crush

Beyonce - Halo
Kelly Clarkson - Already Gone
Jordin Sparks - Battlefield
David Archuleta - Barriers
OneRepublic - All the Right Moves
OneRepublic - Secrets
Natasha Bedingfield - Strip Me

The Veronicas - 4ever
P!nk - U + Ur Hand

Lady GaGa - Just Dance
Lady GaGa - Poker Face

Miley Cyrus - See You Again
Selena Gomez & the Scene - Naturally

The Black Eyed Peas - I Gotta Feeling
Flo Rida - Club Can't Handle Me
David Guetta - Gettin' Over You (intro and parts similar to intro only)

Rihanna - Only Girl (bridge only)
Rihanna - Disturbia

Kevin Rudolf - You Make the Rain Fall
Flo Rida - Right Round

Shontelle - Perfect Nightmare (specifically the "no way" part)
Lady GaGa - Telephone

Katy Perry - California Gurls
Ke$ha - TiK ToK

Taylor Swift - Mine
Taylor Swift - Love Story

Janelle Monae's "Cold War" sounds like a mashup of Outkast's "B.O.B." and Gnarls Barkley's "Going On."

madonna like a prayer - Abba Sos
lady gaga alejandro - Abba fernando (alejandro is clearly an homage to sweden music .. abba and ace of base.. infact redone is swedish )

Rihanna - Unfaithful and Rob Thomas - Lonely No More, when it comes to the chorus

4ever and Ur + Ur hand so right, i remember when pink came out with the single everyone was going on about her copying 4ever

Ohh. And am i the only one who see's this:

Theory Of A Deadman - End Of The Summer and Nickelback - Photograph

They have the same exact guitar chords and similar bridge melodies.

Wow, I have never thought of this one before! They do sound a lot alike!