Calvin and Hobbes (with an essss) at the end

My mom got Cayden a Calvin and Hobbes book that had a huge collection of the comic strips in it. She noticed that he liked to read the comics in the newspaper and she figured he might like a book too. Well, he loves it. He has read that book cover to cover more times than I can count. Today, I was at Barnes and Noble and there was another one in the Bargain Book Section so I picked it up. He is currently in his room and I think it will be hard to get him to put it down. The funniest part is that he calls them Calvin and Hobbes (esss). I've told him a couple of times that isn't how you pronounce it but now I just let it be because it is cute!