5. Carl Carlson
One of Homer's closest friends (and fellow Power Plant employees), Carl has been a big part of The Simpsons since early in its history. So why kill him off? Personally, I think he'd be a very interesting character to kill off in terms of how it would effect the rest of the cast. Homer - and to a lesser extent, Marge - would obviously be devastated, but also I can't help but wonder what would happen to Lenny. Carl and Lenny have been associated with each other since they made their respective debuts, and if one lost the other I don't know what would happen! And seeming as Lenny is safe as he doesn't meet the "Emmy-winning" requirement, Carl would be the one to sign out of Springfield for good. How would Carl go, though? Would it make sense story-telling wise? Well, as a long time worker at the Springfield Nuclear Power Plant - a place with infamously bad health and safety measures - it wouldn't be out of the question that there would be some kind of radiation leak leaving Carl in a critical condition. The only problem is that this would be a dark, painful way to go, and something I think even Groening's team would struggle to make light of. Carl is definitely a character residing deep in the danger zone, so Carlson fans beware!