There is a great series of pictures of the animators using a model to get their drawings of Disney’s Alice correct:
http://www.boredpanda.com/alice-wonderland-drawing-animation-technique-kathryn-beaumont/
Another post Bored Panda has is a hilarious post with animators modeling faces for their animations:
http://www.boredpanda.com/mirror-facial-expression-disney-animator/