Here are some good animation pencils in various stages of clean up and in assorted styles.
What makes them good is not the quality of each individual line itself, but rather the ability of all the lines to contain the forms within them. All these pencils reveal that the artists understand that the characters are made of forms that all make sense and fit into a plan that adds up to instant recognition of a character and a statement of attitude or emotion.
Too many modern cartoonists think that having a perfectly clean line is the end goal of a good drawing - even if the forms within the clean lines are vague, unbalanced or wobbly.
I like pencil lines that have feeling and understanding like these.
In all these drawings, the first thing we see is the characters themselves, not the line quality.
The lines are subservient to the characters.
In this Jiminy Cricket drawing you can see the rough flowing shapes underneath and the line of action and direction of each of the forms. The clean lines on top follow along those underlying principles and don't fight them.
Even in this very clean and tight Jetsons drawing, you can feel the forms underneath.
These Bickenbach drawings show that the characters, while somewhat stylized, still follow some logic. The shapes are pulled along the line of action and overall pose. Then the lines are stretched around the line of action and forms.
All these skills and concepts go back to the early rounded animation forms.
Even this later complex Chuck Jones style uses all the same principles. The lines on Witch Hazel all describe distinct clear shapes which in turn fit into the larger forms. They all fit together and make an instantly readable character and pose and expression.
Scribbly Pencils
These drawings show me that the artist has trouble understanding and defining forms. This is too vague and scribbly to be of much use to the next artist down the line.
I've seen some modern character designers who draw like this, with lots of squiggly 's' curves that don't add up to any clear forms or overall plan. There are even "how to" books that attempt to explain that drawing sloppy is a good way to become a designer. Why anyone would need a book to teach you how to be sloppy is beyond me but these books definitely exist. I'll give you a tip for free: Step on your fingers for a few minutes before you do your next drawings and you will get some nice vague scribbles when you try to draw something.
Modern Cold PencilsThis style of clean up seems totally divorced from classic cartoon drawing principles. I have to stare at the images for awhile and make them come together in my head to form a vague character image. They don't appear alive or committed to a statement like all the drawings above.
They just seem like random jumbles of lines with no distinct plan underneath. The eye wanders around the puzzle of lines. It doesn't help that the lines are all one skinny even width. There is no construction, no hierarchy and all the angles veer off into contradictory directions. It looks like connect the dots.