The original Menaechmus is a wealthy citizen of Epidamnus who was kidnapped as a child and separated from his family. He inherited his fortune from his adoptive father and maintains a high status in the city as a patron to several clients. Feeling constrained by his marriage and civic duties, he seeks pleasure outside his home. He is an epicure who prioritizes food, wine, and his lover over his domestic obligations.

Originally named Sosicles, he was renamed in memory of his lost twin brother. He has spent six years traveling across Italy and Greece in a relentless search for his sibling. Unmarried and unattached to civic duties, he acts as a free tourist who adapts quickly to confusing situations. He is highly opportunistic and readily takes advantage of the free meals offered to him by strangers.

A young man whose name translates to "sponge," Peniculus acts as a professional flatterer. He attaches himself to wealthy men, offering them praise and running errands in exchange for lavish meals. He owns very little himself and bases his entire identity on his relationship with his current patron. He views public duties as an irritating distraction from eating and drinking.

A wealthy woman who brought a substantial dowry to her marriage. She keeps strict tabs on her household and expects her husband to report his whereabouts constantly. Her controlling nature pushes her husband away, leading to a highly hostile domestic environment. She frequently laments her situation and views herself as a woeful victim of his bad behavior.

Erotium is a flirtatious prostitute living next door to Menaechmus. Her name translates to "pleasure," and her household serves as a relaxed, luxurious alternative to the strict rules of her neighbor's home. She uses seductive language to draw men in and is highly motivated by gifts and financial gain.

Cylindrus is an enslaved cook owned by Erotium. He takes immense pride in his culinary skills and speaks in a wordy, grandiose manner. Familiar with the eating habits of regular guests, he knows exactly how much food to prepare to satisfy large appetites.

Messenio is an enslaved man forced to travel extensively across the Mediterranean. He acts as the archetype of the honest servant, carefully guarding the travel funds and offering practical advice. He fears physical punishment and strictly follows orders to avoid beatings or starvation.

The father of Menaechmus's wife is an elderly citizen who relies heavily on a walking stick. He acts as an authority figure in family disputes, though he admits that wealthy wives are often overly demanding. Despite his attempts to mediate fairly, he quickly becomes frightened and confused when conversations turn aggressive.

A highly confident medical professional who boasts that he could heal the gods themselves. He struts confidently into the street and speaks in clipped, jargon-heavy sentences. He insists on gathering direct facts to make rapid diagnoses but lacks the courage to handle genuinely chaotic patients.