if someone does If U Seek Amy I will 

 .... can you imagine them singing F-U-C-K Me on Idol?  lmao.... I hope someone performs Circus, Sober, Halo, Gotta Be Somebody..... 
songs I would advise against singing (just because I could see someone butchering them totally)..... Gives You Hell, Miley Cyrus songs, Katy Perry songs, any of the rap / hip hop songs.