Do you remember the movie Final Fantasy - The Spirits Within or The Polar Express?  If so, you may have experienced Uncanny Valley due to the realism of the characters. 

Uncanny Valley is a psychological phenomenon describing the eeriness or discomforting feeling one gets while observing an object that mimics a "human" but is not quite "human enough".  In 1970, Masahiro Mori, a robticist, coined the term in a Japanese magazine Energy titled "Bukimi No Tani".  The article explains his observations while working with humanlike robots.  You can read the translated (English) article @ The Uncanny Valley.

Some of you may experience "Bukimi no tani" while watching the PS3 demo of "Heavy Rain" - http://en.wikipedia.org/wiki/Heavy_Rain

References:
http://www.theuncannyvalley.org/
http://en.wikipedia.org/wiki/Uncanny_valley