O. Henry, "The Ransom of Red Chief" (1910) from The 50 Funniest American Writers: An Anthology of Humor from Mark Twain to The Onion:
Has anyone in America not read "The Ransom of Red Chief"? In my experience, this was a story that I've chuckled over from elementary school to now, in settings both academic and informal. As an allusion, it's cultural capital is slightly below "The Gift of the Magi"--but only somewhat.
I can barely bring myself to recap or comment on the story, since it seems so well worn to me. But, since I've started noting some of the similarities between horror and humor, I will add that O. Henry's stories demonstrate one aspect shared by both: the use of anticipation and surprise. In horror, that surprise takes the form of "oh no," whereas comedy's use of surprise is more like "oh no he didn't." (Drama's use of surprise is less necessary to the effect of drama; though if I had to put it in this form, I'd say it more often takes the form of "he didn't!" Especially in Henry James, where the reader's next line is, "Wait, what did he do?")
So O. Henry will start with his scenario--two men kidnapping a boy--but he'll front load that story with hints that things didn't turn out quite the way we expect them to. From the first line--"It looked like a good thing: but wait till I tell you"--our anticipation is stoked to a point where he can then drop the boom on us. It's the kind of lesson that makes me want to get back into comedy writing.