Japan is a country featured prominently in the episodes "Chinpokomon", "A Ladder to Heaven", "Pinewood Derby", and "Whale Whores". It consists of an archipelago of four islands of the coast of East-Asia in the Pacific. It is neighbors with China, North Korea and South Korea to the west.
In the late 1990's a Japanese toy company created a franchise dubbed Chinpokomon (a parody of the real life franchise by Nintendo, Pokemon), where the company attempted to use various products including toys, a television show and a video game in an attempt to brainwash American children into joining their army and have revenge on The United States of America for the effects of the post-World War II occupation of Japan.
In response to the boys building a ladder to Heaven, the Japanese build their own ladder to compete with and to beat the U.S. to heaven. The ladder is built exponentially fast, quickly extending into space and "growing by 1000 miles every day". After a few days, they announce on the news they have reached Heaven and that they claim it as part of Japan because "they got there first". Although it was obvious that the "Heaven" they broadcasted was really a studio imitation that quickly fell apart, it was enough to convince the U.S. that Heaven exists and that they were beaten to the punch.
The Japanese are depicted as having a vendetta against dolphins and whales, constantly killing them in zoos, aquariums, and the ocean, because they initially believe that they caused pain, psychological trauma and misery to the people in Japan by piloting the Enola Gay, the plane that dropped the atomic bomb Little Boy on the city of Hiroshima. They came to that conclusion when the American leaders during World War II delivered the Japanese government a photograph showing the "pilots" of the Enola Gay, with a dolphin as the pilot and an Orca as the co-pilot. Upon being arrested by the Japanese government for using aggressive methods to prevent the country's whaling attempts, Stan phoned Kyle and asked him to photo-shop a new picture with the "real" pilots of the Enola Gay being a cow and a chicken. The Japanese become outraged at the cows and chickens for "framing" the innocent whales and dolphins and then they turn their focus on slaughtering cows and chickens on farms. The Japanese depicted are frequently stereotyped, killing the cetaceans with use of spears and kamikazes. The current Emperor of Japan is Akihito. The Japanese are notably always depicted speaking actual, correct Japanese, likely due to the fact that Trey Parker is a fluent Japanese speaker.