He is Giulia and Massimo Marcovaldo's pet cat. He is also one of the first to know Luca and Alberto's secret of the two being sea monsters after Luca inadvertently spat his water onto Alberto's face, revealing some of his sea monster form.
Machiavelli is a burly cat with black and white fur (white fur for front half, and black fur for back half). He has black ears, a black muzzle, and a black patch of fur on his front left leg, and the entire back half of his body white.
His name was revealed on the Funko Pop! box for Giulia.