In my opinion, it could either harm or help the show. Sometimes, you need to change a show to make it better. However, lot's of shows end up jumping the shark with these sorts of things, simply because they changed it in a way that no one wanted it to change. A character's death has a big impact on a show, and a safer alternative would be, simply, to change something else. However, with Family Guy, even though I don't watch it, I know that there isn't much to change. In a Drama, killing off a character, if done properly, works. But you don't watch a comedy for it's story, at least not Western Animation. Well, maybe, but you can't very well have it take over the show, which is what killing off a character will end up doing. Now, I know I am going off topic with this last part, but changing a big part of a comedy usually gets people upset. Which is why it is a better idea to do something that will change it, but not too much. Take for instance, PHineas and Ferb. There are a lot of things in that show that you could change, but they would mess up the story a lot. So, they made a less important character find out one of these things, that Perry was an agent. It changes things enough to make it better, but not too much that it ruins it.
