Percy's Squeak! is a read-and-colour magazine story.
Percy hardly ever needs repairing and is always ready for work. But one day, Percy heard a peculiar squeaking noise whilst shunting trucks in the yard. The trucks tease him, telling him that he sounds like a mouse. Percy felt very embarrassed. Eventually the Fat Controller asks the maintenance staff to have a look at Percy. They give Percy an oil, but find nothing wrong with him and the troublesome squeaking remains with him.
That night, Percy and the other engines tried to go to sleep, but Percy's squeaking kept everyone awake. Percy was still squeaking in the morning when his driver arrived. The Fat Controller tells Percy not to work until the squeaking noise goes away and the driver and fireman agree to give Percy one final check. At last the fireman opened the boiler and the squeaking noise became louder. The fireman started laughing, then the driver went to look and started laughing too. The driver and fireman then held up four tiny mice. The trucks had been right and all of the engines laughed, even Percy.
- The plot is similar and may have even been the basis for the sixth season episode, Thomas, Percy and the Squeak.