Arguably, just as important as Monkey is Ratboy from Ratboy Is Dead. Most definitely one of my oldest characters, and like most people in the comic, was originally based off a real person (though almost all resemblance to that person is now gone save for some highly charactured traits).
Ratboy is kind, extremely loyal to his friends - his only friends, Marvin and T.J.J. Ratboy is also not quite sure where his fantasy role-playing games mystical universes end and reality begins. Or why he keeps dying. Or why nobody else will tolerate him.