J. K. Rowling works to dispel our preconceived notions about the Harry Potter characters and about the magical world that they inhabit. Her presentation of the merpeople is one example of challenging a façade. She plays to our expectations with a beautiful, shapely, stereotypical mermaid in the painting in the prefects' bathroom; then, underwater, she reveals a village of hideous creatures with long, green, tangled hair, sallow gray skin, broken yellow teeth, and eerie appearances. They are not remotely what we think Harry will find at the bottom of the lake, and they are not supposed to be, for even mythology must have its secrets, and even Harry, who is still learning about the wizard world, has his own, often misguided, notions about how things should be. The same is true of Mad-Eye Moody, who is among Harry's favorite teachers before he reveals himself to be the villain responsible for placing Harry directly within Voldemort's line of fire. Again, Snape proves himself to be innocent, although all of the signs point otherwise. Almost nothing in this book is what it seems, teaching the reader not to jump to conclusions, but to gather evidence slowly and to prepare to expect the unexpected.