Wonder Girls is coming back with a new sound - and it's something you may not have expected!

You thought they were coming back with another groovy and retro sound, but according to this new MV teaser for "Why So Lonely," they're going... reggae?  Looks like HaHa will be happy about the recent surge in popularity of reggae-inspired music.

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The sound is very nice, but the visuals is what's even more interesting!  The girls look gorgeous and mysterious outdoors, even slamming a trunk on a bloody arm.  What might the full MV be about?  Stay tuned!