Since "The Grim Adventures of Billy and Mandy" has been spun off from "Grim and Evil", it is a much better show. This deserves to be on its own.
The premise is unusual. Billy (an idiotic little boy) and Mandy (a dark, sarcastic girl) trick Grim (aka Death), who has come for their gerbil, into being their "best friend forever". The show is a series of adventures of the two with their tall, dark and boney "friend".
This is apparently not everyone's cup of tea. The reaction to this show is very strong. Some hate it, some (like me) love it, especially with the rather morbid sense of humor that Mandy has. At the start of every show, Mandy gives a little comment, often relating to the episodes in the show. My favorite is "Evolution takes no prisoners". I'd like that on a bumper sticker!
My only complaint is...Why does Grim/Death have a Jamaican accent?
All in all, if you like "The Addams family", you'll get a kick out of this show.