When imps are summoned into our world and bound, there is a magical compression that happens to them. What results is the lovable little tricksters, like Greg. Big Greg is an imp in his true form, released from the compression of his binding.

Believe it or not, Big Greg is still the exact same imp as his tiny form, just capable of doing a lot more damage if Duncan orders him to. He might look scary as hell, but he’s still his obnoxious, annoying, lovable self.