They spend years amassing a fortune and then retire. The rat becomes obsessed with learning and buys many books to read. He also compiled many works himself. He also educates the six former lizards in various arts and they all are successful. After awhile the rat and four of the lizards die leaving only two of the band alive. These two fail to live within their means and are forced to once again steal to make their way. They wind up stealing a pair of Cinderella's slippers and one takes all the blame and is killed. The other does not live much longer himself.
The story is a fairy tale for a couple of reasons. There are elements of magic and a surprising ending. The whole story is based on the fact that the story of Cinderella occurred and the fairy godmother did in fact change the animals into men. This is obviously a magical feat. Also, the fact that the animals have human equivalent intelligence is unrealistic and so fairytale-esque in that it personifies the personalities of the transformed coachman and footmen.
Also, at the end of the tale, the reader is told that the fuzzy slippers taken by the two footmen are now on display at a museum in Pittsburgh and are being called pin trays. This is offering a fantastical explanation for the actual objects at the museum.