Bart Junior's offspring, eating the crops of Australia

Bart Junior was a frog that Bart caught. It was later brought over to Australia but was released into the wild since Bart was not allowed to bring in foreign animals. Bart placed it in a fountain outside of the customs planning to pick it up on the way home. However, it jumped out of a window and was taken away by a kangaroo. The next day the entire of Australia was infested with Bullfrogs, all which were the offspring of Bart Junior.