Nantucket is a young teenage mouse male with pale grey fur and a white patch around his mouth.
He wears a white dress shirt, a green plaid short sleeve sweater, a dark red tie, dark grey pants and pocket, and white loafers with a red stripe.
Later, he is seen during the Feast of St. Squeaky, hovering near a table covered with various cheeses. He sword fights against his brother Tweeds using a fondue skewer.
When the family begins to sing about the cat king, Tweeds sings about stabbing the tyrannical King Puss Puss and then pretends to run his sword through Nantucket, who collapses onto the table and throws handfuls of red confetti while the rest of Ralph's family cheers.
The next day, when Princess Carolyn and Ralph are leaving Stilton Acres, he is seen standing beside Tweeds, and waves goodbye to them as Ralph places the last of their luggage in his car.
- During Feast at Stilton Acres, Nantucket presumably plays King Puss Puss in the reenactment of his defeat.