...is mad, lives in a cave, and throws rocks at anyone who asks him where his ideas come from.
...has long gray hair and looks a stylized father time garden gnome. 
...passes unnoticed among you
and may have brushed your coat once in passing. 
...doesn't try to be funny but sometimes is. 
...hears voices that speak poetry but don't slow down so he can copy it. 
...has been known to write a story or two...