If I do PPL ground school online, do I have to do all of it?
You need at least 40 hours of ground school, according to the Transport Canada regulations (421.26). So you will need some sort of evidence to show that you have done so.

I do hope that you weren't seriously considering doing this. Please read the answers to this question. 

You will see a common theme - most accidents are caused by the pilots themselves. Knowing aviation theory inside and out is the best protection you have against joining them in those statistics. It is not a stretch to say that your life depends on the attitude you bring to your flight - starting from the first lesson of ground school.