Answer:
I jump when I walk and sit when I stand. What am I?
I have more shoes than anybody but less feet than everyone. I am met in the morning but departed in the night. I may shake as if I'm angry but I won't bite.
I'm as simple as a circle worthless as a leader; but when I follow a group their strength increases tenfold. By myself I'm practically nothing.
I come with a train and go with a train and the train doesn't need me but can't go without me.
Brown I am and much admired. Many horses have I tried. Tire a horse and worry a man, tell me this riddle if you can. What am I?
The negative hero in each story