Deathly Hallows part II epilogue

in the epilogue of the deathly hallows 2 it shows in a cage a tọc mạch, chồn, ferret pet. in the beginning of the series, only 4 pets r allowed in hogwarts; rat, toad, owl, cat. if u look at the Harry Potter RPG spot, ull see that one of the characters has a pet marten, which looks like a ferret. in the movie inkheart, they use a tọc mạch, chồn, ferret to play a marten. coinsidence?