I have had discussions with people who insist that karpas must be a small piece of diced vegetable (i.e. smaller than a ke-zayith le-Humrah), dipped in salt water, and nothing more.
When I then ask what the practical purpose of doing that is and if they think that the authors of the haggadah had such a thing in mind, they cannot give me an answer.
So, what is the practical purpose of karpas? Is it really just to eat a fleck of salty celery and to move on?