There's always three NPCs at the pizza/cake shops; the one in the front always gives you a candle, the second one always gives you a stamp (get three and trade them for a set of their clothes in whatever colour), and the one in the back sells shit. In other words, by the time you get sick of the candles and buy all their stuff (the inventory does change/update!), you'll only still want the stamps really. Unless you don't want any more of their outfits either of course.