One day you may be tempted to write a novel about, say a man who can turn into a dog, a weredog, if you will. Once you realize that, hey, this story is pretty cool, you may think it is funny to name your character something cute, like, I don’t know, Rex. And then you may decide to name your novel the very amusing title, Rex Appeal after your cleverly named main character.
If you do that, you should know that for the next months, and even years of your life you’ll be forced to write weirdly convoluted sentences in order avoid using your character’s name in a possessive manner. Because “Rex’s bowl” or “Rex’s room” or “Rex’s fur” just doesn’t sound or look correct.
But it is and you have to use it, because it’s grammar, dammit.