That's a pretty silly thing to say, I don't think you thought it through.
AC works exactly the same as DC until you get tied up with the complecities of power factor.
If they were all wired in series the voltage would depend on what else you have connected and all the plugs would have to have something connected for anything to work.
Connecting loads in series done with a constant current supply, for example a LED lighting system might use one switching power supply which produces a constant current of 325mA - to increase the load you add more LEDs in series.