Puns about dolphins often refer to one's purpose in life. Instead of using the word purpose, the word "porpoise" is used in reference to the marine mammal in the same family as dolphins. One example is a pun about buying a glass dolphin: "Life can be so confusing. It was only after purchasing a dolphin made of glass that I had any clarity of porpoise."
Another pun involves the story of researchers who captured a porpoise with feet. Before releasing it, one of the researchers suggested they cut off the animal's feet so it would look similar to the other porpoises. The doctor in the group disagreed, stating that doing such a thing would be "defeeting the porpoise."
Although the word "porpoise" is commonly used to refer to dolphins, the porpoise is actually an entirely different animal. It is found in the order Cetacea and belongs to the Phocoenidae family. Physical differences distinguish the two. The porpoise has a shorter beak than a dolphin. Dolphins have conical teeth while porpoises have flattened, spade-shaped teeth. Despite these differences, the terms porpoise and dolphin are still used interchangeably even by sailors or fishermen, especially when referring to small dolphins because of the two species' similarity of body shape.