I added the car to the world train set animation.
I continued with the Udemy course. Starting to actually make something like a character.
We added an empty which is a an non-rendered object that we parented the eyes and head. We were then supposed to animate a ball using an empty but I decided to animate the head.
I watched some more of the DIY Engineering covering catapults. Over several lectures it covered the ballista, trebuchet and onager.