I would like to see Trader Joe's stylesheet/writing manual. You can find a lot of similarities in Trader Joe's quarterly newsletter to Groupon's tounge in cheek writing. I have always thought that Trader Joe's pioneered this sort of marketing. In fact, if you read their newsletters, you'll also see cute illustrations of animals posing questions or asides.
For example: "Much as Hemingway captured the spirit of Paris in the 20’s, Trader Joe’s Pork Roast Florentine captures the spirit of, well, roast pork on your dining table. (You didn’t think we’d compare ourselves to Hemingway, did you?)"