This is for those submissions of small size, yet great inspirational value.
This looks like an elaborately fashioned wooden egg-cup, but it is a powerful magical tool, used mainly by witches to conjure up spirits and familiars.
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.