For genearlly lighthearted fantasy that dives into deep waters unexpectedly, it's hard to beat Terry Pratchet's Discworld series.
Discworld extracts
On a vampire who has turned into a bat in order to spy on a couple of old women, but tragically forgot to take into account a vital aspect of the local environment:
Vampires have risen from the dead, the grave and the crypt, but have never managed it from the cat.
On the nature of Darkness:
Light thinks it travels faster than anything but it's wrong. No matter how fast light travels it finds the darkness has always got there first, and is waiting for it.
On the philosophy of witches:
'Witches just aren't like that,' said Magrat. 'We live in harmony with the great cycles of Nature, and do no harm to anyone, and it's wicked of them to say we don't. We ought to fill their bones with hot lead.'
On Psychology:
Granny Weatherwax had never heard of psychology and would have no truck with it even if she had. There are some arts too black even for a witch.
On Atheism:
Besides, when you hit your thumb with an eight-pound hammer it's nice to be able to blaspheme. It takes a very special and strong minded kind of atheist to jump up and down with their hand clasped under their other armpit and shout, 'Oh, random-fluctuations-in-the-space-time-continuum!' or 'Aaargh, primitive-and-out-moded-concept on a crutch!'
Folk wisdom:
Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life.
More cat stuff:
Nanny Ogg also kept a cat, a huge one-eyed gray tom called Greebo who . . . opened his eye like a yellow window into Hell.
And of course, quotes from “Good Old Bill Door” (who always speaks in capitals):
IT'S BECAUSE OF THE UNCERTAINITY PRINCIPLE.
'What's that?'
I'M NOT SURE.
---
THERE IS NO JUSTICE, THERE IS JUST US.
---
'Are you Death?'
IT'S THE SCYTHE, ISN'T IT? PEOPLE ALWAYS NOTICE THE SCYTHE.
Finaly, a personal favorite, Granny Weatherwax, a “Good Witch” has a decades-delayed confrontation with her evil sister Lily, as we learn that witches apparently come in pairs – a good one and a bad one:
Granny stepped forward, her eyes two sapphires of bitterness.
"I'm goin' to give you the hidin' our Mam never gave you, Lily Weatherwax. Not with magic, not with headology, not with a stick like our Dad had, aye, and used a fair bit as I recall - but with skin. And not because you was the bad one. Not because you meddled with stories. Everyone has a path they got to tread. But because, and I wants you to understand this prop'ly, after you went I had to be the good one. You had all the fun. An' there's no way I can make you pay for that Lily, but I'm surely goin' to give it a try."
