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