Katy Perry Tweeted THIS PHOTO from American Idol.

Buy the exact same dress here:
She is wearing the Alaïa Ruched croc-effect vinyl halterneck midi dress. Buy it HERE!
Get the look for less here:
#KatyPerry #AmericanIdol #halterneckdress #halterdress #mididress #leatherdress #vinyldress #alaia