Springfield is one of television's most densely built places. Behind almost every line of dialogue there is a sign, a storefront, a product, or a citizen who exists for a single beat and is never named again - and the show trusts you to catch it, or not.
Much of the comedy lives in the background. Duff on tap and a Krusty-branded product for every possible occasion; the Kwik-E-Mart and its permanently expired inventory; a monorail nobody asked for. A great deal of it flickers past in one frame, engineered for the pause button and the rewind - jokes designed to reward the viewer who looks twice.
The oddest of these fixtures tend to outlast the plots that carried them. A throwaway prop, glimpsed once, becomes a piece of folklore that fans quote decades later, long after the episode around it has faded. Springfield is a town that runs on disposable detail, and somehow the disposable detail is what sticks.