Muggleborns and Halfbloods trying to be like Sherlock and completely failing
Muggleborn: Well, it's obvious that he has a cat at home, you can see the hairs on his everyday clothes, and it's ginger, meaning he has an orange cat and his name is Whiskers
Person muggleborn is talking about: Those are my hairs, I don't have a cat, I'm allergic
*Muggleborns and Halfbloods start laughing and one wheezes: Sherlock can be wrong sometimes*