Understand the stereotype of a creep.

To creep is to move slowly and quietly as if sneaking up on someone. A person who's creepy is someone who's perceived to be eerily quiet in some way, as if there's something behind the scenes that could surprise you in an unpleasant way. Think of a cult leader, serial killer, child molester, prostitute, or stalker. They all have a dark side brewing that they keep tucked away until the right opportunity comes along. And if you're coming off as creepy, it means you're doing some of the things that strange people often do. Other creepy behavior includes laughing or smiling at unacceptable moments, or perhaps finding humor where others find sadness.