10 Artists Who Sang Back Up For Britney Spears

As it turns out, a lot of people have collaborated with Britney Spears. And interestingly enough, a lot of prominent singers have lent their vocals to the singer -- appearing on a number of her tracks, including "Piece of Me" and "Lucky." It makes you wonder what the song would have sounded like if they had taken over. But alas, we'll never know.

1. Bonnie McKee, "Ooh La La"

The singer is the same writer responsible for practically all of Katy Perry's hits. McKee and Perry secretly sang background vocals on the Smurfs 2 track.

2. Justin Timberlake, "What It's Like To Be Me"

Back when JT and Spears were dating, he and Wade Robinson co-wrote a track for her third album. Oh the good ole days.

3. Katy Perry, "Ooh La La"

See Bonnie McKee.

4. Keri Hilson, "Break The Ice" and  "Gimme More"

This Beyonce shade queen penned two tracks for Blackout and ended up singing back up for the pop star.

5. Ke$ha, "Lace And Leather" 

While Ke$ha wrote "Til The World Ends" she only appears on the remix version. She's only on this track because of her go-to collaborator, Dr. Luke, wrote the song.

6. LMFAO, "Lucky"

This is baffling to all of us.

7. Miike Snow, "Piece Of Me" 

Miike Snow aka Bloodshy & Avant aka Christian Karlsson and Pontus Winnberg wrote and produced songs on a number of Spears' albums, including Blackout, Circus and Femme Fatale.

8. R. Kelly, "Outrageous" 

Like many singers who wrote a song for Spears, Kelly ended up doing backing vocals for the singer.

9. Robyn, "Piece Of Me"

Robyn sang the demo and Spears and crew ended up keeping her vocals in the background.

10. Sabi, "(Drop Dead) Beautiful"

This budding pop star was handpicked by Spears to appear on the track. The singer drops a verse in the song as well as provides backing vocals to the star herself.

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[Photo: Getty]