Penguin? is typically confused and sometimes feels that they might better be associated as a green kappa monster.  Seen here, Penguin? appears to be a normal but possibly still confused penguin.

Who is/are Sumikkogurashi? 

“Sumikkogurashi” are the characters living a quiet and solitary life in the corner. They might be able to settle down when they’re in their corners but, they don’t like being in the center of the room. When they’re taken to the center of the room, they always rush back to the corner.