EMO rarely needs to be rebooted, but if for some reason you need to, you can do so with a paper clip. Simply use the paper clip to GENTLY press into the left hand of the two centre holes as highlighted below in the picture. This will shut him down. Then place him back on the charger to trigger him to power up again.
DO NOT PRESS ANY OTHER HOLES AS YOU WILL DAMAGE EMO.
What do the other holes do? Check out this article here