"... every Monday these same oranges and lemons left his back door in a pyramid of pulpless halves."
I warned you I was going to do this. Come on. Play along. (And, no, I wasn't thinking about Andy Kaufman when I dreamed this up. It was all a riff on that Baz Luhrmann trailer for the new "Great Gatsby" movie.)
So, now, let's talk about oranges and lemons. The phrase "oranges and lemons" appears twice in the sentence, unchanged, even as the oranges and lemons themselves are changed. That's the whole action of the sentence, the transformation of oranges and lemons in one form into oranges and lemons in another form. Here they are on Friday, in crates, and here they are on Monday in "a pyramid." That is, they have become, in that alluded-to time period — the weekend — a pile of garbage. But the pile is called "a pyramid," A pyramid! We're called upon to think of the grand erections of pharaohs, in comparison to crates from the lowly little character with the silly-sounding occupation "fruiterer."
Are the crates even stacked up? There's the absurd and obviously false notion that the fruit has been improved by whatever it was that went on in that house over the weekend. That absurdity calls upon us to think about the people who arrived and left, the people who ate all that fruit. But of course, they didn't eat it. They drank it. The pulp was extracted for use in alcoholic mixtures, and if the fruit emerged from the weekend as "pulpless halves," then, we may infer, so did the people. We don't hesitate to keep calling them human, yet we see the inaptness of calling the mere rinds "lemons and oranges." Even if you could conceptualize the big pile of rinds as a pyramid, you'd easily perceive it as garbage. Since that perception is easy, we have energy left to think about what is more difficult. Who are these people?