Have you ever thought your roommate was a werewolf? Well, I have. And not because she was particularly hairy at certain points, although that may have added to my suspicions. No, it was because one night, my junior year of college, she crept out of bed (I know, because I was sleeping beneath her) and quietly left the apartment. Now, this may not sound like unusual behavior for many students, but it was for her! And for me, that was enough to conclude that she was, in fact, a werewolf. As I lay there, it began to occur to me that she probably knew the moon was coming out from behind a cloud. She would have had to get out of there or after her transformation, she would have bitten and even killed the rest of us in the room. My poor friend, I thought, having to live with this all her life. Worrying that she'd do harm to those around her, never breathing a word of her terrible secret.
However, I did have some doubts. Could I possibly have jumped to a conclusion without checking all the facts? To ease my mind, I knew I had to confirm my suspicions. I crawled out of bed and went to my computer. I searched for moon phases; I needed to know if that night was a full moon! Looking back, I realize I could have just as easily peered out the window, but I didn't seem to have much common sense that night. Finally, I found what I was looking for and breathed a sigh of relief. She couldn't possibly be a werewolf because it was only the quarter moon. I went back to bed and peacefully fell asleep in the knowledge that I wouldn't be bitten and have to live out the rest of my own life as a werewolf.
(To be fair, I had just finished HP book three... Harry learns Remus Lupin is a werewolf. Although, is that really enough reason to make me think that my friend was too?)