And a person appears out of thin air, not all at once but in stages, building himself from the inside out. Very quickly, but not too quickly for a vampire's sight to catch the intermediary stages.

He has the Joker's scars.

He is wearing a little black dress not dissimilar to Queenie's, or at least, he is once it assembles itself on top of his skin; last of all, a nametag sticks itself to his chest, declaring him to be a Whistle whom you can call Ghosty.

"Boo," he chirps.