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Demi Lovato has a mystery collaboration in the works.  The pop star posted a photo on Instagram in the studio recording what she called a "killer duet."  The photo shows both her and her unknown musical partner holding thumbs up signs. 

It led many of her followers on an Internet hunt to identify the body attached to the hand in the photo. 

One popular theory is Nick Jonas.  MTV says Nick was seen wearing a similar shirt in the photo the same day it was taken, and also notes that Demi mentioned working with the youngest JoBro in a recent interview.  Nick was also the creative director of her recent "Neon Lights" tour. 

Who do you think it could be?!

Photo: Getty Images