Pop Goes the Diesel is the twelfth episode ever made in Season 2.
Duck the Great Western engine works very hard on the Island of Sodor and everything goes smoothly when he is around. He can keep the coaches quiet, the trucks behaving, and the passengers happy. He is also very proud of his Great Western heritage and talks endlessly about it, which irritates the larger engines who quickly grow tired of hearing about "the Great Western way".
One day, a visitor arrives in the shed. The Fat Controller introduces the new engine as Diesel, stating that he is given a trial and charges Duck with showing him around and teaching him what to do. Diesel introduces himself before heaping compliments on Gordon, James, and Henry, which quickly win them around to the newcomer. Duck, however, takes a dislike to Diesel's oily nature and shows him to the yard.
There it becomes apparant that Duck's dislike of Diesel is mutual as Duck orders Diesel to refer to the Fat Contoller as "Sir Topham Hatt", before Diesel smugly tells Duck that he does not have to be taught what to do. As a Diesel, he already knows everything and that Diesels will always improve a yard. Duck is cross about this and orders Diesel to arrange the trucks while he leaves to take Gordon's coaches to the station.
Diesel, eager for the chance to show off, quickly gets to work. However, he attempts to move the wrong trucks; some really old ones which have stiff joints and brakes. When Diesel cannot move them, he tries getting very forceful with them. Duck arrives, and realises what is happening, but decides to let events pay out. Diesel gets so frustrated with the trucks that he accidentally overturns some when their brakes snap. Diesel still cannot move the remaining trucks and is forced to give up.
Duck finally comes forward carrying some other trucks and Diesel asks Duck why he did not tell him about the others. Duck simply reminds Diesel that he was supposed to instantly improve the yard. Duck leaves happily, while Diesel fumes.
Diesel is later forced to help clean up the mess, a duty that he hates especially as the trucks have started teasing and singing at him. When the clean-up is over, Diesel, now cross with the trucks and with Duck, storms off back to the shed.
- In the scene where Duck is exactly side-on, a small space between the face and the model is visible.