Do snakes, scorpions and other Aussie wildlife go into houses in the Aussie cities?

While it's not a regular thing,it does happen occasionally.We had a snake trying to get in our back door recently & had it not been for the quick thinking of my granddaughter it would have.We live on a 5 acre block in N.W.Sydney & there are lots of wild animals & snakes in the gully behind us so it's reasonable to expect them to come near the house.I found a possum in the family room one morning! He came in the cats door,lol. However,we haven't had an alligator in our pool as I heard one American family did recently, & the sharks stay in their own territory.