I imagine that, when a celebrity or a "celebrity" chooses to appear on Big Brother, their agent spends some time telling them, "Remember you're on TV. Remember you're on TV. Remember you're on TV. Don't let it slip your mind for a moment. You're on TV. TV! The public can see you. Remember that."
I have this image in my mind of the agent staring at the TV over the subsequent weeks and repeatedly smacking their head off the nearest hard surface.