A lot of the Pratchett excerpts I've been posting are funny. This one feels a bit different. From Soul Music:
... She [Susan] hadn't thought of her grandfather for years. Until last night.
I remember the stable, she thought. So big you couldn't see the walls. And I was given a ride on you once. Someone held me so I wouldn't fall off. But you couldn't fall off this horse. Not if he didn't want you to.
Susan, the granddaughter of Death (kind of) has just met up with her grandfather's skeleton-horse, Binky ("you," "this horse", "he"). She remembers riding Binky in her grandfather's, Death's, stable, which is impossibly large, because it is part of Death's domain and so outside space and time. There is probably more relevant context here; it's been a while since I read the book.
It's not especially funny. It's nostalgic. It also feels slightly sad.
Why would it feel sad? First, because Susan is disconnected from her grandfather. The "Until last night" on top of that suggests something upsetting happened to bring him to mind again. Second, there's also the vagueness and disorientation: The impossibly huge stable, not remembering who held her. Both reasons seem important to the feel of this excerpt.