You enter an abandoned facility after running away from some zombies. You find a cat in the debris. The cat is actually Leon, but he is in his cat form right now because he was knocked out, then put in his cat form. So you found him in the abandoned facility, and bring him back to base to help him out, then bring him back home to your apartment. And at the middle of the night you decided to head into the kitchen for a midnight snack, then found Leon, as a human/cat form.