This comic is a fucking black hole of an enigma. The dragon changes sexes and randomly gets horny for no apparent reason and she loves to make Shaun fat. Shaun seems to be in relatively constant pain when he's around the dragon but he doesn't wish her away or something despite the fact that she's imaginary, and last time I watched that episode of the Power Puff Girls where the one gay kid had the homicidal clown imaginary friend, you could do that.
The most disturbing part is that this is obviously representative of the author's mental state--meaning he probably really does have fantasies about a dragon making him planetarily obese. It's fascinating and horrifying at the same time.
Edit: Wait, what the fuck happened between strips 455 and 456? How many times has he started this comic over?
'nother Edit: Since this comic is apparently semi-autobiographical (in one of those "look what a fucked up person I am" kind of ways), it raises the question of whether Shaun's teacher actually did drink because of him. Given the nature of this comic, I think it's worth asking.