How about this for a philosophical question...
Do animated characters "act"? And what about animators? Do we "act"?
Acting, by definition, is when a person pretends to behave like another person in another place at another time. Even if they're pretending to be themselves in a real place we are still stuck with a person pretending to live a moment that does not currently exist. All acting comes down to a falsehood. A false person, a false place or a false moment. One or more of the three. Acting is pretending. Without pretending you don't have acting.
So when I am animating, am I "acting"? Not really. When I animate I am not pretending to be a character in some other moment in some imaginary place. I make no pretense about it- I am Keith, sitting at my desk animating this scene.
Similarly the character on the screen is not pretending to be anything, either. Bugs Bunny running away from Elmer Fudd is Bugs Bunny running away from Elmer Fudd. He is not pretending to be Bugs Bunny running away from Elmer Fudd. The animated character is not pretending- they are just being themselves*. This is their life, this is their moment and there's nothing false about it.
As an animator am I pretending to be Bugs Bunny? Aside from the physical difficulties of such a thing, not really. So what is it that I'm doing if I'm not 'acting'? I prefer to think of it as imagining. I am most successful when I can simply imagine the character just being themselves in whatever moment of their lives that I am called upon to animate. The key to this is to know the character. That's it. Insofar as I struggle to express a character believably it shows that I don't really know that character. Want proof? OK, try this....
Think of someone you know very well. Then imagine they are running late for work and have just hit their 5th red light in a row. You can see them, can't you? You can imagine exactly what the look on their face would be, how their hands would be gripping the steering wheel- what they'd do and how they'd behave while they wait for that light to change to green. And you know that what you are 'seeing' in your mind's eye is not what you would do in that moment, but it is what this person you know very well would do. They have unique actions, mannerisms, expressions and gestures that you don't use, but you can "see" them. At this very moment I can imagine my Dad in the situation I just described and I can see him as clear as day, how he'd act and everything- and he's been dead for 8 years. Today my Dad is no more physically real on this earth than Bugs Bunny- but as a character he's very real and I know him very well.
And this isn't hard at all. Why? Because I've already known how to do this from the time I was a kid. And so do you.
The hard part in this comes when a character hasn't been defined very well for you by the director/writer/story people. You don't have enough to get to 'know' the character. Or worse, we're too lazy to get to know the character. It's at that moment that we fall back on generic gestures or expressions, or we copy ourselves acting just to get some believable motion on the screen. To me that's a poorer solution compared to the power of knowing the character. In animation if we had characters that were more clearly defined and the imagination to see them being themselves, then perhaps we can maybe break free from the generic "everything same" characters we are so prone to make.
* OK, exception would be when Bugs Bunny dresses in drag to fool Elmer Fudd. So in that sense, yes an animated character does "act".