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.
A ghost is haunting someone with a secret-it\'s not that he murdered the person that became a ghost, it\'s that he went into hiding with a new identity to avoid being murdered, whilst the ghost wants him to join her in the afterlife. The ghost is getting stronger and more dangerous each day. Enter the PCs.