The pay-off to an elaborate set-up tale, giving a pun on a familiar expression (in this case a song title). From Vince the Sign Guy: Vince Rozmiarek of Indian Hills CO and (from his Facebook page) “his lighthearted puns shown on local community signs”:

Phonologically, there’s a stretch of speech that’s both I herd it through the grapevines (the pun, the pay-off from the vineyard cow story) and the nearly homophonous “I Heard It Through the Grapevine” (the model, the song title); semiotically, however, that stretch of speech is either about one of these situations or the other, not two nearly identical situations
Specifically, there’s no metaphorical structuring of the vineyard cow situation (in the story) on the basis of the information exchange situation (in the song). Their only relationship is phonological.
This isn’t a defect; most puns are merely phonological, and that’s fine. Vince Rozmiarek’s vineyard cow story is a great little joke, of a recognizable genre of punning: the set-up + pay-off story based on a formulaic expression — for short, a formula pun.
It’s just that a small number of puns are what I’ve sometimes called — I’ve wrestled a long time with ways of saying this — satisfying, meaning semiotically satisfying: the participants are represented as belonging to two worlds at once. They are anteaters, say, with the formicavore’s passionate hunger for the insects, but they are also diners in conventional American restaurants, insisting on specific kinds of table service and exhibiting dining quirks (like an aversion to spicy food). The first of these worlds is systematically mapped into the second, in an elaborate metaphor. (The restaurant-going anteaters are a recurring theme in Bizarro cartoons.)
From this month in my postings: on 8/3 “Brief shot: cock time”, about the expression cock time:
An atrocious pun [on clock time], but satisfying in that some … item is not merely introduced into a context for a near-homophone, but participates in the world of that model expression. We see something that’s a cock [a man’s penis] and a (kind of) clock.
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