Legal Question in Landlord & Tenant Law in California

It seems you do not understand what a demurrer is. A demurrer is a motion for a court order that a complaint be amended or dismissed because even if everything in it is true, and even without regard for any possible defenses, it wouldn't entitle the plaintiff to win as a matter of law. So if you think about it you should see that it is impossible to file a demurrer until you have received the complaint and know whether or not it alleges facts that constitute a cause of action or not. That is true in all civil cases, including UD.