The episode begins with a bathroom products race between Bart and Lisa in the bathroom sink. Lisa wins and Bart suggests she won because her shampoo was in the "inner lane" to his toothpaste. Lisa explains the Coriolis Effect to her brother (not entirely correctly), but he doesn't believe her. He makes a collect call to an Australian boy (after calling many other Southern Hemisphere countries, like Argentina and a fictional African dictatorship, without getting an answer), and asks him about which way the water drains. The line is kept open for several hours. When Bart doesn't hang up, the Australian boy's father is billed $900.00. The man wants Bart to pay, but he rudely mocks him. Bart receives dozens of collection letters in the mail, but does nothing about them.
Eventually, Australia indicts Bart for fraud. The United States State Department wants to send him to prison for 5 years, but settles upon having Bart personally apologize in Australia. The family is sent to Australia, where they start exploring the culture. Bart brings a bullfrog with him and puts in a fountain because he doesn't want to get into more trouble and promises to come back to get the frog. The frog runs off and meets a kangaroo and goes into the kangaroo's pouch. On the way in, Homer sees a marine at the American Embassy and mistakes the marine to be a Queen's Guard and makes fun of him and so then gets knocked out. Later, when Homer leaves the embassy, the marine reveals that the embassy is American land and Homer jumps in between the countries and gets knocked out by the marine again. Marge and Lisa go to a museum, where they see Australia's first Prime Minister who looks like Snake. Then Marge warns Lisa to take care of her camera. Bart goes to the courts and makes his apology, but they want to give the additional punishment of a boot to his butt (a parody of the Michael P. Fay caning incident in Singapore). Homer and Bart escape the booting and gets chased back to the embassy. The American Embassy tries to keep out the Simpsons, but fails due to a malfunction from the gate and after the Simpsons come in the soldiers close the gate manually keeping out the enraged Australians. Bart agrees to a booting from the Australian Prime Minister, but with a normal shoe and only once; however, as he is about to receive his punishment, he dodges the kick from the Prime Minister. Then Bart moons the Australians with the words "don't tread on me" written on his butt and hums "The Star-Spangled Banner." The Australians break down the gate and chases the Simpsons and the Simpson family leaves the outraged country in a helicopter in a scene similar to the Fall of Saigon with the Austraian throwing Fosters at the Simpsons. A subplot through the episode where Bart brought his pet bullfrog into the country past customs, where it reproduces and spreads rapidly throughout the country and ruins Australia's ecology (a reference to the actual introduction of non-native Cane Toads into Australia).
As the family is being flown home, they happily remark upon the destruction that can be caused by introducing a foreign species into a new environment - as the camera pans out to reveal a koala hanging from one of the helicopter's struts. The camera zooms in on the koala, ending with a close-up of its eye, implying that America will face a similar threat to Australia.
In Australia, the episode was met with criticism due to its hugely inaccurate and stereotypical portrayal of the country, although it has been accepted as typical American satire and is still aired as a re-run as often as all other episodes. Some Australian fans of the series rather consider it an honor that Australia was featured so much in an episode at all. Subsequent Simpsons episodes exploited existing stereotypes of other countries, but this episode actually fabricated things about Australia wholesale, as the Simpsons producers admit in the DVD commentary for this episode.