They are vaguely humanoid creatures with a pair of arms and legs, but no face. Instead, their heads have large cavities through them that resemble the eye of a needle. They appear in a variety of forms, depending on the environment they live in. The regular Pirori that inhabit the Barracks Settlement are a deep shade of mauve, whereas the Sewer Pirori are a much paler shade, possibly an adaptation to the lack of sunlight. In the FC World B, Pirori take on an 8-bit style appearance and are more grey in color.
Sewer Pirori seem to be the biggest ones out of the three types.
When Madotsuki interacts with Pirori, they respond by making a three-note chime that varies in tone between individuals. In the FC World B, they make a more muted, 8-bit tone, and sewer Pirori are silent.
In addition, some Pirori have the ability to teleport Madotsuki. In the Barracks settlement, one Pirori is randomly selected per dream to take Madotsuki to the Pirori territory in the FC World. The lone Pirori in The Docks B will send Madotsuki into The Wilderness just outside of the Barracks Settlement.