It's a bit of a misconception that anything can happen in a wonder tale, especially in a version by the Grimms... remember, their training was as lawyers, and they were retelling the stories as German propaganda -- to promote rationality and other social values they deemed "proper" (their heroines got meeker and more dutiful in each subsequent edition, for example [in my retellings, they're shifting back to the uppity end of the spectrum]).

Yes, magical things happen, but there is a logic behind every one of them. Every good deed is rewarded, bad deeds are punished, and the punishments fit the crimes... and creatures generally remain true to their basic natures. The birds who help Aschenputtel (Cinderella, or Ashley Pelt) get her work done in time to go to the ball, for example, do so in a very bird-like way: pecking at seeds and ash -- no Disney-fied singing mice in sight!