Sometimes walking through a moldering old crypt can be a pleasure. With the smell of bone dust and ancient burial wrappings, almost like a library. Certainly as quiet. Until you step in a patch of Choo Mold.
In the middle of an unimportant combat with some bandits a burst of wild magic transforms all of the PCs and their opponents in to random animals and monsters. They retain their intelligence (though not, of course, the ability of speech). They can either carry on the combat in their new forms, panic, or otherwise react how they see best. After about an hour, they return, unharmed, to their normal form.