Final answer:
Pufferfish, also known as fugu, is a delicacy in Japan that requires chefs to pass a rigorous exam for a license due to the fish's toxicity.
Step-by-step explanation:
In Japan, a chef must pass a national exam for a license to serve pufferfish, which is also known by the four-letter name fugu. This practice is in place due to the high levels of a potent toxin called tetrodotoxin found in the fish. The licensing exam is rigorous and involves identification of the species, proper preparation techniques, and disposal methods to ensure that the poisonous parts of the fish do not contaminate the edible parts. Serving fugu is a cultural tradition in Japan, where it is considered a delicacy and where the risks involved with its consumption are taken very seriously.