The idea is for each character to look very whimsical and flowing. It is basically wild and wavy hair in the wind. It has a very organic and Art Nouveau feel to it.
References:
Image sources:
http://www.taaz.com/beauty/images/stories/featured/how_to_get_wavy_hair_wavy_hairstyles_waves.jpg
http://farm1.static.flickr.com/88/213126369_e82dd8ec12.jpg
http://www.ecosalon.com/wp-content/uploads/2009/06/long-hair-blowing-in-wind.jpg
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