While in the bathroom, Bart notices that the water in the sink always drains counterclockwise. Lisa explains that the water never drains the other way except in the southern hemisphere, due to the Coriolis effect, but Bart does not believe her. To confirm this, Bart makes phone calls to various countries in the southern hemisphere. Lisa points out how expensive international calls are, so Bart decides to make a collect call instead. He calls Australia, where a little boy answers the phone. Pretending to represent the "International Drainage Commission", Bart is informed that the toilet and sink are both draining clockwise. Frustrated, Bart asks him to go and check the toilets of the neighbors. The call takes six hours to complete, since the boy lives in the outback, and Bart forgets to hang up the phone. Later, the boy's father is billed AUD$900. The father calls Bart and demands that he pay, but Bart only taunts him. Unfortunately for Bart, the father's neighbor is a federal Member of Parliament, who reports Bart's offense to the Prime Minister.
After a long series of ignored letters, Australia indicts Bart for fraud. The United States Department of State wants to send him to prison in order to placate the Australian government, but Marge furiously objects to this idea. The State Department then settles on having Bart publicly apologize in Australia. The family is sent to Australia. They stay in the American Embassy which is fitted with all the comforts of their home country, including a specially modified toilet that overcomes an exaggerated Coriolis effect. Then they start exploring the local culture.
After Bart makes his apology, the parliament reveals that they want to give him the additional punishment of a "booting", which is a kick in the buttocks using a giant boot. Bart and Homer escape and the family flees to the American Embassy. After a prolonged standoff, the two governments propose a compromise to the Simpson family: one kick from the Prime Minister, through the gate of the embassy, with a regular shoe. Marge is opposed to the idea, but Bart agrees. Just as he is about to receive his punishment, he moons the Australians with the words "don't tread on me" written on his buttocks, then hums "The Star Spangled Banner". The Simpson family flee the outraged country in a helicopter. As they fly away from Australia they see that due to a bullfrog Bart left earlier at the airport, bullfrogs have begun to overpopulate and destroy the Australian ecosystem. Viewing the devastation, the family remark upon the destruction that can be caused by introducing a foreign species into a new environment, and laugh at the Australians' misfortune, unaware that a koala is hanging onto the helicopter, implying America will face a similar fate.
