Who Is The Greatest CGI Character Of Them All?

There have been countless characters in movies and television generated entirely using computer effects. But which one was the most believable as a character?

This isn't a poll about which CGI creature looks the coolest - instead, we're aiming at which one felt the most like an actual character in the movie. In other words, which one made you forget you were watching CGI? Which stirred up your sympathy?