My little pet peeves from what I've seen.
Monotone voice WOULD be nice, but it usually sounds terrible.
Just a voice without much emotion, cold, would probably be a better instruction.
If it were possible to edit the sound post-production to make the voice more robotic rather than depending on the person to do it(badly), that would be ideal, but hey, that's just dreaming.
Getting them to stutter or repeat words sometimes (without the typical stressd-out voice of a stuttering person) would be very robotic.
Or just repeat all short words 3 times, " a..a..a.." or "the...the...the..." whenever they come up in the sentence would be an easy little instruction, maybe. This changes " I can't move my arm" to "I..I..I.. can't move my..my..my.. arm." Very robotic, even if the voice is kept full of emotion as normal.
In another scenario, an emotional "human" reaction to a draining battery could be cool.
Robotic movement basically depends on the person, and it seems that most people suck. Oh well

For people without the skills of a mime, the occaisional robo-twitch would be a better effect than trying to do the arms-bent robo walk.
I'd love to see someone with even half the skill of Shields and Yarnell, though.
A 2 person game could be just like the touch-freeze game, except the challenge is to push the "power switch" (back of the neck, base of the back, whatever) to turn someone "off". But they can try to dodge or block the attempts. Could get rough if the players are too competitive.
A funny ending to the session might be convincing the person that the only reason they've been hypnotizable all along is because they actually ARE robots, but never knew it. But if they find out they're actually robots, they will become confused and freeze up.
And last of all, I'd rather see a good-looking or even nicely plain woman fully clothed,or half-clothed

instead of a not-so-hot one willing to get naked.
To be blunt, the #1 part of the robot fantasy includes the concept that nobody would build an ugly, chunky gynoid.