Answer:
There are several different kinds, but the one you pick doesn't do its job. What is it?
An iron horse with a flaxen tail. The faster the horse runs, the shorter his tail becomes.
What is that over the head and under the hat?
What is long and slim, works in light. Has but one eye, and an awful bite?
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
People take me on walks and I run and have fun. What am I?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?