Not pukas that can turn into horses (or, occasionally, rabbits) or other such beings. Human beings who can change shape. Dove-maidens and swan-maidens, and rarer birds like spoonbills and golden peahens, straight ouf of fairy tales. Selkies. Werewolves and other wolf changers. I think there are bear-shifters. . . .even though in fairy tales they are only one person, cursed, well, so too are there cursed wolves in fairy tales. Same goes for frogs.
Off in the Far East, of course, you get animals changing to humans, but I think if that gets mentioned at all in the tale, it's going to be a far off and strange thing.
Witches' habits of turning to cats or hares might come up, but might not.
But reading folklore in general has not left me with a deep well of shape-shifters to draw upon
Perhaps I need to do more research into the folklore