The cabbage slug is a tiny brown and white creature with very fast reproductive abilities. In a group, it can destroy entire cabbage patches in less than a week. This pest is sometimes hard to spot as it bores holes into cabbages and eats them from the inside out, so by the time its presence is realized, it is often too late to salvage the vegetation. As a result, a single cabbage slug could destroy the entire ecosystem of a city.
One of these creatures had nested itself in the cabbages that the cabbage merchant intended on ferrying over to Ba Sing Se to trade there. However, the passport attendant of Full Moon Bay denied the crops as a precautionary measure, fearing that they may be infested with cabbage slugs, and subsequently ordered their destruction at the jaws of a platypus bear. Her decision was justified when a cabbage slug was flung free from one of the destroyed cabbages.
The real world garden slug enjoys eating cabbages and other leafy crops. Slugs, which are similar to snails without shells, are a type of mollusk related to clams and oysters, though most slugs live on land. Because they are prone to drying out and subsequently dying, they secrete a slimy mucus coating, feed at night or on rainy days, and take shelter during the heat of the day. They tend to hide in moist, dark, cool places, such as under rocks and boards and in piles of decaying organic matter.