Bart vs. Australia

The bullfrogs taking over Australia and destroying all the crops is a reference to the cane toad, originally introduced to Australia in order to protect sugar canes from the cane beetle, but became a pest in the country.

The main premise, which is that the "Coriolis effect" causes all drains in a certain hemisphere to rotate a certain way, is in fact not true. The Coriolis force is too weak to cause any visible effect, and the water can rotate in any direction anywhere on Earth. The direction is primarily determined by the shape of the vessel and the way it was filled. Ironically, the "hemisphere determination" urban legend is still widely believed because of its use in several fictional works including this very cartoon.