What about Chuck Mangione living in the Megalo Mart on King of the Hill? Malcolm in the Middle also had an episode where a guy was living in the store for years without being detected.
https://m.imdb.com/title/tt0640296/ - not much of a synopsis here, but enough to track down the episode. The guy helps clean and saves one of the characters during his stay between the aisle shelves.
https://en.wikipedia.org/wiki/Malcolm_in_the_Middle
@vgeek If you have more information about the episode I would appreciate that.