The boto of Brazil is a pink river dolphin by day, and a man in a white hat by night.
Your prompt is BOTO.
Visiting by night
The boto wears a white hat
To cover his crimes
His white hat covers up his blowhole, and the legend covers up centuries of violence against women. Read more here.
Sort of on prompt:
Man in the white hat
With matching suit and pale cat!
Beware his dark chat
The cor-de-rosa,
Sly cetacean lycanthrope;
Para menina.