Hey, bad hair days can happen to anyone -- even celebrities. Sure, they've got the big guns styling them for the cameras, but bad decisions have been known to be made.

Stars like Christina Aguilera, Alicia Keys and the ever-experimental Olsen twins have gone down the red carpet with super questionable hairdos that make us cringe, but by the same token, they've also shined with the most glamorous tresses. Check out the good, the bad and the just plain ugly in this Stylelist gallery.

Sure, the 'American Idol' contestants of past and present have shown us they can sing, but what's up with their hair? There have been some serious hair styles gone bad in the talent show series and AOL TV has gathered them all up so we can ask the question: "What were they thinking?" Take a look back at the worst of 'Idol's' hair-don'ts in the gallery below.