Warning: if you are very susceptible to the power of suggestion or have a touch of hypochondria, you might want to skip this video. John Green talks about medical conditions that are so weird, you’d think he was making them up. No, they are real, but most are rare or relatively inconsequential. This is the first of a three-part video series called “Summer Bummers,” which should make you feel lucky to be in as good a shape as you are. If they go a little fast for you, you can find a transcript at mental_floss.