This is the mask of "Arlecchino", best known as Harlequin, probably the most famous Commedia character.
Being one of the servants (also known as "Zanni"), Arlecchino is like a 5-year-old. He is eager to please his master or mistress (one of the lovers, or Pantalone, or La Signora), lives in the present, loves what he sees, forgets what is out of sight. His first attention is to food: how to get it, how to savor it, how to preserve it for later. He loves tricks and physical antics (known as "Lazzi"). He relishes his adroitness at getting out of difficult situations and seldom considers the consequences until it is too late. Never malicious, Arlecchino is sympathetic to everyone's misfortunes, to a fault.
Arlecchino usually cannot read, which makes him confuse messages sent by lovers. He is ignorant yet clever; slow mentally but quick physically. His actions and moods can change in an instant. He may fall in love with Columbina, but it is puppy love, never lustful.
His lower back is arched, and his arms are often bent with hands on his hips, in readiness to serve. His legs turn out in 4th position, sometimes with heels together and other times with the back knee bent and the front leg straight, like a Baroque bow. He runs quickly and lightly, kicking his feet forward. He sneaks to steal food with large, exaggerated, silent steps. He can stop in an instant, especially when caught in one of his pranks. He carries a slapstick, which makes noise when it hits something and serves as a potential weapon, musical instrument, magic wand, eating utensil, or phallus.
A comparable animal image for Arlecchino is an Irish setter puppy.