Changeling
From Tardis Wiki, the free Doctor Who reference
The Changelings were individuals controlled by the Graske that mimicked a lifeform and sent the real one to Griffoth. They looked exactly like the original, but their eyes flashed a greeny-gold colour occasionally, hinting at their true disposition. A Graske created Changeling for a Slitheen, a street Urchin, a Mum and a Dad before they where succesful returned home from Griffoth. (DW: Attack of the Graske)
