Meanwhile, close friends want to distinguish themselves from casual friends, and one of the ways they can do it is by being unfriendly, at least on the surface. When a close friend forgets his wallet and can’t pay for lunch, you might call him an idiot. This works only when you’re so confident of your friendship that you can (playfully) insult him, without worrying that it will jeopardize your friendship. This isn’t something a casual friend can get away with as easily, and it may even serve to bring close friends closer together.