Graske (Attack of the Graske)

A Graske attempted a Graske invasion of Earth by stealing people from various Christmases from across time and replacing them with changelings. (NOTDWU: Attack of the Graske)

Behind the scenes
Attack of the Graske had two endings determining the fate of this Graske after the player operated the Doctor's TARDIS and tracked the Graske to Griffoth; one where the player froze everyone in the room forever, leaving the changelings on Earth, and another where everyone was returned to their rightful place.