> but the mirror hasn't shattered

But it's bent. (Take that in any sense you care to.)

> Is "shatter" the past tense of "shitter"?

As it happens, I saw a Mary Beard programme ("Meet the Emperor") on BBC2 last night, in which she said that Claudius's last words were alleged to have been "Oh dear, I've just shat myself". This may or may not have been due to the poisoned mushroom he'd just eaten, according to some sources, from the fork of his wife.