I don't think this happens in any other country in the world. That is where guests to a party or social gathering may be requested bring some food for the party.
Of course invitations are no longer appended with Ladies bring a plate. Usually I think it is, Please bring a plate.
I know some from other countries or cultures would be very offended by guests bringing anything. Some party givers even provide cigarettes for the guests who attend. Well perhaps that one is not appropriate now.
I wonder if this really is an Australian customs and what are it's origins?