The power switch of the robot may be located anywhere on it's body. The most common places to place a power switch on humanoid robots is behind the hair on top of the head, behind the neck, under the clothes on the back, or behind an openable plastic panel on the back. 

That is because engineers aim to make the robot feel alive, therefore it's important for them to hide the mechanic parts from the eye. 

If you cannot find it on the body, you can ask the robot itself, or try to use a screwdriver to take off different parts until you find it.

I hope this helps!
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