the "Uncanny Valley" is a pscological  phenomenon that descirbes the disgust or fear humans have against almost human looking puppets or robots like this one for example :
its called the uncanny valley beacause of a graph that describes the human reaction about several objects if its only a bit realistic or a real living person we have an positive reaction if it is nearly realistic we have a strong disgust :
this "valley" in the graph is the eponymous valley

there is an 2010 Coca Cola light commercial spot that contains humanoid puppets 
personal i have a strong disgust against this commercial and i met a few people who reacted the same way to this

Now what do you you think about this commerial?
what do you think about humanoid puppets or robots ? do they scare you or not?
and what do you think about the Uncanny Valley itself?

thats really interesting, why do you think polar express caused that? It's not that realistic.... oh and that robot scares me to death...

Interesting theory, where did you here about it? I wonder what actually causes this?
The people from that commercial did look pretty creepy, they reminded me of the characters from that movie 'Carolyn'.

P.S. To all Americans, The USA is the only country that has 'diet' soda, in other countries it is called 'light' soda. I hope this clears up any confusion that people might have.

I can agree about the robot at the top, but I didn't find the commercial creepy. Sure, I felt some disgust against it, but that was because it sucked, not because of the puppets.

What I wonder is why you don't feel like this about today's realistic video game characters. Are they an exception to the graph or something? Personally, I think the graph is just bull****. What I believe is what creeps people out about the robot is this:

It looks real enough for your brain to actually be able to think of it as a human being. However, the brain notices the small details in it's movement, behavior and/or appearance that makes it look non-human, and this causes some dislike, or even fear. Maybe it's some sort of animal instict, to be wary of that which is different, maybe as nature's way to prevent mutations, I don't know, I'm not an expert.

I could try to "prove" this by showing a picture of a scary face which isn't a robot or an animation, like this guy.

That's the Penguin, from Batman. Maybe not the best example, but I'm too lazy to do any real "research".

But then again, this is just something I made up on the spot, at 2:30 AM, with no previous knowledge about the subject, so I could be wrong. I just find it hard to believe that realistic robots, dolls and puppets are scary or disgusting just because they are robots, dolls or puppets, and I don't think the answer is something as simple as a graph. And I personally don't feel any disgust against the Polar Express characters either. Snow White is far creepier than that conductor.

I've seen numerous puppets and dolls that share the appearance of the ones featured in that Coca-Cola commercial that I dislike. I've seen many that look far more realistic than those. Doesn't barely reach the so-called uncanny valley. I have to agree with Zoph.

That first image just looks wrong. Reminds me of a screwed up sculpture. I guess if it's obviously an imitation, feelings of disgust are invoked. The uncanny valley theory is one which I believe to be true. Though, I'm not so sure about the exact cause. I see a few reasons being given when searching the internet.

Each and everyone of us having varying views. I also agree with that instinct thing Mogwai brought up.

Here's some stuff.

knight_34's link gives an explanation that at least I would be willing to accept. For those of you who don't want to read the whole thing, I'll give you some examples.

The Uncanny Valley may be a deep, instinctual reaction: it steers humans, on an automatic level, away from humans who are dead, diseased, or deformed (which is often an indication of poor health).

Warning: Death is bad for your health. Sorry, I'll go back to the quoting.

It may also alert "normal" people to the presence of mental problems which would render someone unfit for inclusion in a peer group. In that way, the theory goes, the Uncanny Valley is a protection against associating with sources of infection.

Skipping ahead a little...

It might also explain the idea of the perfection of the human face. You try drawing a perfectly detailed face, and if there's one thing that's slightly out of place, or if the shadow's just wrong, or there's a small bump where there shouldn't be, the whole face doesn't just look wrong, it just feels wrong, despite it being quite a good drawing nonetheless.

oh come on guy she not that bad just move some stuff around give her a smile and bang perfect

That looks much better Peter. Bravo, great work!

I love how such a Victorian concept is garnering more attention currently through the works of robotics etc.

to clear some things :
neither i have a general disgust against  humanoid robots  nor
im thinking this coca cola commercial is scary
i said it disgusts me
thats why im thinking this is a let me call it an unfortunate advert spot

I've seen numerous puppets and dolls that share the appearance of the ones featured in that Coca-Cola commercial that I dislike. I've seen many that look far more realistic than those. Doesn't barely reach the so-called uncanny valley.

in my opinion these dolls look real enough to reach the uncanny valley they do not have to be perfect
to give an example from tvtropes: a creepy children advertrn
this dolls do not look completly realistic but nevertheless its
an example for the uncanny valley
especially the faces and body proportions in the coca cola commercial are causing my dislike

i first heard about this phenomenon on tvtropes.org (thats the website knight_34 linked above)
but i dont not really agree with that theory about death and healthiness which is mentioned on tvtropes  and brought to us by iMogwai and Zophia
personally i think its not really the disgust against death or rotting flesh but more like an inner feeling that this "uncomplete/ not perfect" artifical "life" is wrong and shouldnt exsist

No, ick, looks wrong, wrooooong!"

but dont misunderstand me like i said above i do not have a general disgust against artifical humanoid beeings
here would be a good point to start philosophizing about the worth of live and ethical problems of robotics or genetic reasearch
at this point Iam not starting this discussion (even if im thinking it would get a very intresting discussion)
but i belive this influences of religion and ethics used in this discussions are similar to those which are leading us to our reaction to objects of the uncanny valley

P.S.: i want to apologize for spelling and grammar  mistakes in my posts im having little problems with these things in any non-native languages