Disclaimer: I am not responsible for any extra, or lack there-of energy charges. Only conduct this if you are the owner of the device. This only assumes that the device will reset back to the correct temp once a valid signal is received. Use at your own risk!!!.
A little trick that i picked up, a bit of a practical joke.
With some air conditioners where the cooling device itself does not have a display but the remote control does:
Try setting the device to a temperature, then take the controller out of the room or cover the wireless thingy that sends the signal (Sorry, forgot the technical name (:TNG)) and change the temperature then wait a few seconds before uncovering the wireless thingy/ walking back into the room.
The air conditioner should be running at the original temperature but the remote controller displays the new temperature.
Great for sending someone crazy.