Piopiota (Nighttime Form)
The lack of sun exposure makes their fur colorless since they only go on dates at night, but it looks kind of cool.
What the Nighttime Form changes
Piopiota is Water. This form adds Dark, so it answers to a different set of matchups from the one you learned on the basic form.
Where Piopiota (Nighttime Form) spawns
This form has no wild spawn point of its own. It comes from an egg, an evolution or an event rather than from walking into the right weather.
Piopiota (Nighttime Form) base stats
A form changes the look and the element, never the numbers. Every form of Piopiota shares one stat line.
HP
102
Attack
108
Defense
99
Magic attack
108
Magic defense
75
Break
50
EP regen
88
The full Piopiota page has the rankings, skills, talents, catch rate and evolutions.