system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we sometimes feel like some bug's crawling on our bodies, but there is nothing there, it's merely a feeling?

Edit: It's not always a static feeling. Sometimes it seems like "some bug" is working (moving) it's way up your body.
gpt
In addition to the other answers here, I'd like to add hallucinations that our jerk brains like to create for seemingly no reason.

People typically have a Hollywood understanding of hallucinations and don't realize how common they are. E.g. how many times have you felt your phone vibrate in your pocket, but when you checked it nothing was there?