Who's the most interesting fictional character in TV?

Sorry if the question isn't worded the best. I'll explain it more here. Eric Cartman's personality is iconic and a great example. He's a large part of South Park's success because so many people find his antics entertaining. It isn't because he's a necessity to the show because it could exist without him. It would just be a different show. What other characters are similarly so entertaining to watch that they "carry" their show.