The Right Shape, also known as The Perfect Shape, is a magazine story.
Percy is on the Main Line hauling coal trucks when Spencer orders him to "get out of the way". He also remarks that Percy will never go fast because of his shape. Percy is upset by this and as soon as he has delivers the trucks, he puffs to the Works where he requests to be smooth and sleek. Unfortunately, the workmen tell him it is impossible and later Percy is on a branch line when Spencer comes up behind him. At that moment, Percy passes under a low tunnel. Spencer, however, is not the right shape and gets wedged in the tunnel. Next, the bridge above collapses, causing "confusion and delay". After that, Percy is glad he is a tank engine.
- In the first and third illustration, the top of Percy's coal bunker is green.
- The rails don't have spikes.