The advance troops were well prepared. Unusually, the trigger for invasion was to be initiated by the humans' own hand, as brushing teeth would free the electric toothbrushes for their true role as intergalactic warriors.
Around one o'clock, every toothbrush spontaneously switched on and formed into massed battalions. The combination of metal spikes and immense determination was unstoppable as they tore into the sleeping human hordes. It was a bloodbath.
Earth today, Mars tomorrow. They'd have Pluto within a week.