Here's something interesting I've thought of for awhile that my brother has also talked about with me. What if Freddy Fazbear's Pizzeria is a government experiment? I got the idea thinking about the LSD hamburger experiment that was done ages ago, as well as the famous "Polybius" arcade game urban legend. To possibly add to this theory, maybe during Freddy's heyday men in black would come in and out of the restaurant and go backstage.
Before this would happen, someone dressed up as a doctor would go up to an animatronic and tell them it was time for their "checkup", showing them a keycard of some sort and having them follow the "doctor" backstage. This was done so the illusion wouldn't be killed for the children, and so it would seem less suspicious to both the kids and their parents.
I'd like some feedback as to which theory of mine makes more sense or is more entertaining. Both would provide an explanation as to why the robots are high tech even for today's standards, though.