Hope that you find the ad funny. If you cant hear all the words, do not blame yourself on that, Australian English is always one of the least comprehensive one in the world. You can see that the dad speaks with a truly Australian accent which is quite rough, unclear and vibrant. There is a joke about the way Australian speak English. It says that they seem to speak English without opening their mouths at all, and it is too prevent flies from getting into their mouths. There are a lot of flies in the country areas of Australia.
Here is script of the ad. Hope that with this, you will enjoy the ad more.
Son: Dad, why did they make the Great Wall of China?
Dad: That was ... during the year, the time of Emperor Nashi Goreng and it was to keep the rabbits here, too many rabbits in China
Teacher's voice: OK, now, Daniel will do his talk on China.
Note: Nashi Goreng is an Indonesian dish and means fried rice. There was not an emperor Nashi Goreng in the history of China and the dad just made it up.