A character in Bram Stoker's novel "Dracula". Renfield is an incarcerated lunatic who serves Count Dracula. He is zoophagus, which means he likes to consume other lives--in Renfield's case, he likes to eat flies, spiders, and sometimes birds.

Personally, I always imagined him as a guy whose exposure to horror has opened his mind to the true nature of the world. He's not insane--he's actually the only completely sane person on the planet. That's why Drac keeps Renfield around--he doesn't really need a servant, but he's not going to refuse the services of an oracle...

Renfield has been played by Dwight Frye in the original "Dracula" and by Tom Waits--let me repeat: Tom Mothafuckin' Waits!--in "Bram Stoker's Dracula".