Prince Serath was looking for the witch's house so he could save the Princess when he tripped and fell into a large and deep mud puddle. But instead of being repulsed by the mud, he found it nice and soothing on his skin. So instead of getting up he relaxed.
Unknown to him, he was beginning to change. First his hands and feet hardened into little hooves. Then his legs reformed to match. After that his maleness shriveled up into his body and became a slit. Then two rows of sow tits grew from his chest. And in just a few minutes, where there was once a prince, was now a sow rolling and oinking in the mud.
Then the Witch decided to release her prized boar into the pen.