Percy's Chocolate Crunch is the eighteenth episode ever made in Season 6.
More often than not, Percy gets the dirty jobs involving trucks and longs for a washdown as much as any engine. However, when he goes to the washdown, Percy and the other engines are informed by the Fat Controller that, due to a water shortage, all engines can only have one wash per day. This annoys Percy as he thinks that Gordon only needs a washdown to feel important. Gordon points that he is important as he pulls the express.
Percy goes back to work, determined not to get dirty. However, that is easier said than done as the trucks give Percy a hard time; they pull him right under the coal hopper. On their way to Callan, the trucks tease Percy by calling him "Dirty Percy". At Callan, Percy shunts the coal trucks into a siding, right alongside Harold who is unloading medical supplies. Harold takes off, spreading cinders and ashes all over Percy. His driver reminds Percy that usefulness comes before cleanliness, but Percy wants a clean job more than anything. The driver suggests taking vans of sugar to the chocolate factory. Percy takes the vans of sugar, feeling happy.
Percy now thinks that he finally has a clean job, but he does not reckon with a patch of oil in the siding leading to the chocolate factory. Percy slips on the oily rails and crashes through the wall right into the chocolate factory and out the other end, covered in sticky chocolate.
When Duck brings Percy back to Tidmouth Sheds, Thomas, James, and Henry tease him saying how chocolatey he is, but Gordon disapproves. The Fat Controller knows how much work Percy had done despite his problems and, as he proved that usefulness comes before cleanliness, Percy is to be rewarded with a washdown and a new coat of paint.
- At the beginning, Clarabel is facing the wrong way and Oliver has Duck's whistle sound.