Frank Kogan

For reference, a selection of roles* portrayed/communicated/inhabited by korean girl group members/artists on singles currently in rotation:

f(x) as the edgy, punk-y youth:
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Narsha (of Brown Eyed Girls fame) as the Madonna/Lady Gaga thought-provoker ( /catchy gibberish chorus provider):
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4MINUTE as the well-known sexy n' dangerous electro vixen:
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IU as the still innocent, young up-and-commer. This song has been a huge hit for the past month:

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Take a look at her interpretation of SNSD's Gee (and Super Junior's Sorry Sorry) for what seems to me like a hint that she'll come to find her own artistic signature soon enough:
http://www.youtube.com/watch?v=EbuSGltOync


* Note how 'concepts', a different word for roles, is (constantly) used when groups come back from a break as a way to frame what new tricks they're bringing to the floor. Sometimes that means 'going dark', 'going hip hop', or just "dressing up in marine/naval outfits" as when SNSD released Genie, but they're almost always given a tag.

Sometimes a group changes styles ever so slightly but remain more or less the same - f(x) have stayed with the spunky, DIY style so far - and sometimes it's a 180 degree turn, a group basically throwing previous musical signatures and image out the door for a try at something else -- see KARA going from cutesy crayola pop to dark and mysterious with single "Lupin". Narsha's development has come off as organic enough: BEG were a fairly anonymous group for years before they found their true selves as sexualized and daring women, and now her solo debut is placed in a quirkier, more adult setting -- no doubt according to her own preferences.