Harry Potter and the Deathly Hallows – Part 1 Kreacher (Simon McBurney)

Kreacher is the house elf who lives at 12 Grimmauld Place. We get way more backstory about him in the book but, for our purposes here, he's notable for finding the thief Mundungus and bringing him to Harry, Ron, and Hermione so they can find out where the Horcrux "RAB" stole is currently located.