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.
Also, when the play ends>
Granny: He done it! We all seed him! He done it with a dagger!
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. When Felmet finally asks Death why he's hanging around if he's not dead, he gets one word in response: Waiting.
The monolith that hides from people.
"Is that a dagger I see before me?" "Um, no, sire, it's a handkerchief. 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!" "...Without what?" "A knocking without the door, idiot." "A knocking without a door? This isn't some kind of Zen, is it?"
The demon summoning scene is funny enough in the book, but gets really funny in the Animated Adaptation, with the demon (easily the best-animated character in the entire adaptation) speaking in a deep, dark and gravelly voice for at first, only to switch over to a high-pitched Upper-Class Twit voice when Granny tells him to stop mucking about.
When the demon reveals its name, which is pretty much a mass of consonants (that Granny still manages to pronounce perfectly, with only a little hesitation!) Nanny has this to say: "Where were you when the vowels were being handed out? Behind the door?"
When the actors in the play the Duke commissioned start forgetting their lines, Tomjon briefly worries he's going to have to do the rest of the play by himself, including a climactic duel with him dramatically parrying his own blows and stabbing himself to death.