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Keith Urban has to be wondering what he has signed himself up for after what happened today at the American Idol auditions here in Charlotte! 

It all began with a difference of opinion over a contestant's performance.  The claws came out, and the fight began!

Nicki Minaj and Mariah Carey had a big fight. So big that Producers ended the auditions early so that the two could cool off.

Supposedly, later on Nicki Minaj even threatened to "knock out" Mariah Carey!  

Take a look at the amature video obtained by TMZ!

Do you think Keith could be rethinking this decision?