Granny Weatherwax's trip to the theater, after refusing to admit that she doesn't quite get the concept.
Someone tapped Granny on the shoulder and a voice said, 'Madam, will you kindly remove your hat?'
Granny turned around very slowly on her stool, as though propelled by hidden motors, and subjected the interrupter to a hundred kilowatt diamond-blue stare. The man wilted under it and sagged back on to his stool, her face following him all the way down.
'No,' she said.
There's a nice Call Back to this many books later in Maskerade, where another man asks Granny the same in the Opera House and she shrugs and does so—he's fated to die the next day, so it's the least she can do.
Possibly made even funnier when she admits to Nanny that she didn't warn him because she could be wrong.
The bit about apple-peeling.
First, [Magrat] had to find out his name. The old peel-the-apple trick should do that. You just peeled an apple, getting one length of peel, and threw the peel behind you; it'd land in the shape of his name. Millions of girls had tried it and been inevitably disappointed, unless the loved one was called Scscs.
Lord Felmet acting like a ghost while Death keeps trying to convince him that he's still alive.
The stone-henge like slab that hides from people.
"Is that a dagger I see before me?" "Um, no, sire, it's a hankerchief. You can tell the difference if you look closely. Not as many sharp edges."
For that matter, all the parodies of Shakespearean dialogue. "There is a knocking without!" "...A knocking without what?" "A knocking without the door, stupid." "A knocking without a door? Is this some kind of Zen?"