How many cats can you fit in one piece of paper?

Do you mean 'How many cats can you draw on a piece of paper'?

It depends on your art style and how big you draw them

So you mean, 'How many cats can stand/sit/lie on a piece of paper at once'?

It depends on the size of the cats, and the size of the paper

actually, any answer to your loose question depends on the size of the paper.