Baby Trains

One day a little boy goes up to his Dad and asks "if big people can have little people and big animals can have little animals, why can't big trains have little trains?"
Dad replies, "Go ask your Mother".
So the little boy goes and finds his Mother and asks "if big people can have little people and big animals can have little animals, why can't big trains have little trains?"
Mom replies "Go ask your Father".
Well, the little boy goes and finds Dad and tells him his Mom sent him back to him. Dad decides a trip to the train depot is in order, so they go on down to the depot and are looking at all the locomotives old and new and the little boy sees a Conductor, he runs up to him and asks "if big people can have little people and big animals can have little animals, why can't big trains have little trains?"
The Conductor says, why son, that's easy, we're Amtrak and we pull out on time.