You are going to deal with someone who may be nice or nasty, but we all do that every day.
If you remain calm and tell the truth then you should have no problem.
I assume you have a flight ticket that shows your onward flight to Australia, if you are civil to the POE officer you should not have a problem.
Make sure that you have a phone number for your parents, immigration may want contact them to verify your story.
What will they want to know?
They will want to know that you can afford to stay in Canada (yes even for one night), they will ask where you are staying, they also want to be certain you will leave (i.e. that you have a ticket, or have the money to buy a ticket).
Look on the bright side.
If they want to detain you, then you will be ready to catch the flight the following day.
If they want to deport you, hope that it is to Australia.
Yes this is humour, lighten up, it should be fine if you tell the truth
