Heres a subject I've always found interesting because of how differing it can be from one person to the next on the basis of our own primal fears.
In 1970, professor Masahiro Mori in japan coined the phrase, because of a study he undertook that looked into the reaction people would have to robots or anatomic constructs and how far along it could go before people would become uncomfortable with them.
lets take an example in robots, androids and cgi characters, robots like Wallie from the movie Wallie, or R2D2 are considered cute robots just about everyone is happy with and feels no anxiety towards.
But then, the next robot we have is something like the robot from I'Robot movie, even if we know its a robot, it has motions to it that are human yet we know its not human, so our brain can quite process it.
And then.. we have the CB2 child robot, a robot made to replicate emotional states of a child, needless to say this thing dips right down into the uncanny valley:
From there, only seeing something like a real baby or a CGI character like the blue monkey people from avatar would pull us back up from the uncanny valley.
Whats interesting about this subject is how really, it applies to a lot more then just animatronics and robots, but to certain primal human fears, that being when you take something your brain registers as something normal, like other human beings, your pets, your home, objects you feel safe with day to day, and then adding something to it that makes it uncomfortable, like imagine if your cat or dog opened the mouths and elongated them to twice the size, that would be a dip into the uncanny valley, or seeing photos of your loved ones, but there eyes have all turned black, again, taking the thing you take comfort from, and it turning into something your uncomfortable with.
Like Gonzo with real eyes, or what if homer simpson looked more real.
(Its like tim curry looking right at me)