"American Idol's" Crystal Bowersox and Siobhan Magnus' outrageous 'dos.

We're not sure what was up with Crystal Bowersox's hair last night -- still in dreadlocks, pulled up and sticking out all over -- but it doesn't really matter because her voice owned the "American Idol" stage when she sang an emotional "People Get Ready". After breaking down at the end of the song, Bowersox received a standing ovation from judge Randy Jackson. Even Simon Cowell said her performance was "inspirational" -- which was quite fitting considering the theme of the night was inspirational songs.

Then there was Siobhan Magnus. Her hair was equally as strange and even included a feather headband to coordinate with the paper butterflies that were stuck to her body. The judges didn't think her rendition of Mariah Carey and Whitney Houston's "When You Believe" wasn't quite "believable", and Simon even commented that Magnus' fluttering accessories looked like leaves and were distracting.

Alicia Keys rocks coily curls on American Idol.

But the woman whose looks really stole the show last night was guest mentor, Alicia Keys. We can't help it, but we keep on falling for the soul songstress's hair no matter what style she chooses. With looks that range from super straight to Bo Derek-style braids to long, flowing curls, Keys always manages to look stunning.

While her hair is naturally wavy, it still takes a good bit of work to get it that way, according to Avon Global Stylist Advisor, Tippi Shorter, who styles Keys' lovely locks.

Shorter told BellaSugar.com, "If you have either naturally curly hair like she [Alicia] does, or if you have straight hair, what we do from the shampoo and conditioning, is we start to use products that help to enhance waves. Once the conditioner has been rinsed out, I'll use something like a volumizing mousse and I will put her hair in about three or four braids. Because we're under time constraints, I will run a blow-dryer up and down her braids just to help dry it, but it's something you can do overnight and let it dry. And once you take the braids out, you have gorgeous waves."

Whose hairstyle do you think rocked the stage last night? And if you missed last week's "American Idol" 'Do Review, check out Adam Lambert's OMG hair!