This type of theme is known as a "chain" or "shared center." The first and second words of each theme entry form a familiar phrase, and the second and third words also form a familiar phrase (which has nothing to do with the first phrase). So the two outer words "share" the center word. This type of theme is somewhat out of fashion with editors (as David mentioned to me in his acceptance message). This one escaped rejection because it has two elements that are not always seen in such themes: 1) The theme entries are related (the first two-word phrase is a household item), and 2) the entries are humorously clued as if the whole three-word set is a thing, thus turning it into a pun, which could be considered the "subtheme" of the puzzle.