Living in your own head! Oh... did I say that out loud?!
When I was a kid, I read all the time, especially after I got glasses, copped some teasing at school, and started to retreat into my shell. Unfortunately I also had the talent of blurting out whatever I was thinking, which usually made no sense to anyone else, but was a result of my overactive imagination at work!
Making up your own worlds and characters is the best... once you learn how to keep the fictional and real worlds apart ;)