I'm finding some of the classic tales are making me laugh out loud as I read them. In some cases I reckon its deliberate - there's a comic undertone to stories like The Brave Little Tailor, or Donkeyskin, where the fairy godmother actually gets things wrong and it says: "The goddaughter did not feel much faith in the fairy after her two previous failures."
But sometimes the humour is unintentional - maybe its related to what one's been drinking:):
“Here," said he, "are the keys of the two great wardrobes, wherein I have my best furniture; these are of my silver and gold plate, which is not every day in use; these open my strong boxes, which hold my money, both gold and silver; these my caskets of jewels; and this is the master-key to all my apartments. But for this little one here, it is the key of the closet at the end of the great gallery on the ground floor. Open them all; go into all and every one of them, except that little closet, which I forbid you, and forbid it in such a manner that, if you happen to open it, there's nothing but what you may expect from my just anger and resentment."
Like - we've seen the trailers dude! We know whats going to happen!
Or sometimes a description adds insult to injury: "Her own daughter, who was as hideous as night and had only one eye" (italics mine !)
Of course, there is a dark side to many fairytales - but finding humour in them has been been a minor revelation to me.