So… Hades, the god of the Underworld, named his dog ‘Spot’?
Yes. I’ve read this elsewhere.
In this famous Greek vase Kerberos isn’t depicted as spotted, but the snakes attached to him* are.
*Snakes are a common attribute of “underworld” figures. I know of no text that describes Kerberos as being covered by snakes, Medusa-like, but you can see it in depictions like this