The Right Shape, also known as The Perfect Shape, is a magazine story.
Percy was 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 was upset by this and as soon as he had delivered the trucks, he puffed to the Works where he requests to be smooth and sleek. Unfortunately, the workmen tell him it is impossible and later Percy was on a branch line when Spencer came up behind him. At that moment, Percy passed under a low tunnel. Spencer, however, was not the right shape and gets wedged in the tunnel. Next, the bridge above collapses, causing "confusion and delay". After that, Percy was glad he was a tank engine.
- In the first and third illustration, the top of Percy's coal bunker is green.
- The rails don't have spikes.