"What if it's the cops?" is a ritualistic phrase which is pronounced at certain times in Australian culture
Primarily, it is used when the occupants of a house are doing something illegal in that house, and there is a knock on the door. Common examples of activities which would require occupants to utter this phrase are:
Especially, this phrase is at it's most appropriate when there is a knock on your door, and just under the ceiling of your house is gathered a huge amount of smoke, signifying that you have been feeding your head.
Australian culture incorporates a healthy distrust of authority, and being able to get away with blue murder right under the eyes of the police is definitely part of this.
With this in mind, directly after you have uttered this phrase, you should follow the ritual and look wildly around the room for evidence of your deeds.
When you have spotted the evidence, you should attempt to place it in a place where it is not obvious to anyone entering the room. For example, if your crime includes smoking illegal drugs, you should attempt to douse them in the toilet. If you're plotting a communist revolution, it's probably best to try and pretend that those machine guns are relics from your service in the Vietnam war.
Of course, if you have large suitcases of cash, it's best to simply keep them handy. In this case, if it is the police, you can simply offer them some money. It is customary for them to ignore whatever you are doing if you offer them enough.
There are of course special rules relating to different states of Australia. If you're living in Victoria, and you think the police are at your door, immediately jump out of the window. The Victorian police are known for shooting before asking questions.
If you're in Queensland, while it's more likely that it's actually the police at your door, it's also more likely that they have come to sell you drugs rather than arrest you for possessing them.
I hope this node helps you acclimatise to Australian culture. We are a complicated but mainly friendly bunch.