|Season Four, Episode|
|Air date||Saturday 2nd February, 2013|
|Post and Prejudice||The Lucky Ones|
Bad Apple is the feature-length episode about the events of 1957, where Diesel comes to Sodor and frames Duck.
Bear returns from Crovan's Gate to Tidmouth Sheds after having his torque converter repaired. James is pleased to see him, and confesses to Bear that his first experience with a Diesel was far from pleasant. Diesel speaks up about the incident and Bear asks what he did that was so bad. Diesel recounts the story, in 1957.
It begins on the western region of the railway where Diesel is shunting, and needs a free siding, but the steam engine due to take the train has had trouble getting steam up. D261 arrives and Diesel explains what's happening, and D261 tells him that steam engines are unreliable and inefficient and that diesels are revolutionary. Later on, Diesel's controller tells him that he is going to go to the Island of Sodor, as Sir Topham Hatt agreed to give a diesel engine a trial. The next day, he travels to Sodor, albeit a little reluctant due to the nature of the Island's main means of propulsion. Diesel arrives at the sheds and The Fat Controller introduces him to the other engines. He assigns Duck to work with Diesel in the yard, and Duck asks him to collect his trucks while he collected Gordon's coaches. When Duck returns, Diesel fails to pull some old ones from a siding, so the trucks begin to tease and sing at him. Diesel is angry at Duck, because he thinks Duck made them laugh at him on purpose. Diesel is eager to get back at Duck, but he needs a plan to do it.
The next day, Henry is pulling some trucks down Gordon's Hill, when they push him and his wheels lock in place once the breaks are applied. At the bottom, Henry's driver tells him he has 'flat tyres', as his wheels have become straightened at the bottom, and will need to go to the works. Diesel arrives with the breakdown train and helps Henry to the works. On the return journey, it begins to rain and Diesel spots Gordon coming in the opposite direction. Due to Gordon's boiler temperature, the raindrops evaporate and it makes him look like a 'sizzling sausage'. Upon this revelation, Diesel begins to formulate a plan to get back at Duck.
The next day, James arrives in the yard to take a long train of trucks, and one of them asks if he will need 'Old Iron's help up the hill'. James is angered by this, and takes the train reluctantly. Diesel asks a nearby truck what the others were referring to, and he tells him the story of Edward lassoing James with rope after he became a runaway. Diesel now has all three nicknames for the big engines, so he passes them around the yard, telling the trucks at Duck told him the names. When the engines come through the yard, they are unpleasantly surprised with rude names, that supposedly came from Duck. The tender engines block Duck out of the shed when he returns home, and The Fat Controller comes to stop the noise. Duck claims he is innocent, but The Fat Controller sends him to Edward's station for a few days, and Diesel is also sent to help on Thomas' Branch Line.
While on the branch line, Diesel notices that the runs up to the quarry are inefficient, as the law states only engines with cowcatchers and side plates can travel up the line. That night in the sheds, Thomas and Toby tell him about Thomas' run-in with the police, and how the law existed for a while put was never actually put into action. The next day, Percy is in Knapford Yard, having his doubts about the situation at hand. He investigates the matter but collecting a list of all of the trucks in the yard when the name calling started. Thomas arrives and the two play good cop, bad cop, to determine the origin of the nicknames. A brake van tells them that Diesel had told them the names, and that he had heard them from Duck.
Meanwhile, Diesel is taking a train of quarry supplies up to Ffarquhar when the points are set to the quarry tramway, and not the yard. Diesel thinks that they want him to go straight through, but he is stopped on his journey by a policeman. The Fat Controller is called and he arrives on Toby. The policeman tells him that Diesel didn't know the law existed, and after Diesel is allowed through Toby tells The Fat Controller that Diesel wasn't telling the truth. Once they arrive back at Ffarquhar, The Fat Controller receives a couple of messages; one being Thomas and Percy finding out the trucks heard the names from Diesel, and another saying that Duck has crashed into a barber shop. Diesel arrives back and The Fat Controller scolds him after finding out that Diesel framed Duck, and he is sent packing. Diesel concludes the story with an apology to Henry, Gordon and James.
The engines accept the apology and Gordon reveals that Diesel's class is now obsolete, as he once saw one of his brothers being cut up for scrap. James uses the opportunity to apologise to Bear for being hostile, and all of the engines are happy to be friends.
- Troublesome Trucks
- The Spiteful Brake Van
- Sir Charles Topham Hatt
- British Railways Controller
- The Policeman
- Oliver (cameo)
- Eric (cameo)
- Barry (cameo)
- This is the last episode to feature a Railway Series story as a plot.
- This is based on the book Duck and the Diesel Engine plus the 1990-1992 annuals by Christopher Awdry.
- Railway Series references include; Trouble in the Shed, Pop Goes the Diesel, Dirty Work, Old Iron, Duck Takes Charge, Thomas in Trouble and A Close Shave.
- This is the only appearance that D261 makes in Sodor: The Early Years.
- This is the first episode to use Alice and Bear's new baked models.
- Barry makes a cameo appearance, but isn't introduced until the episode after, The Lucky Ones. Oliver also makes an appearance on his old branch line before it was closed.
- An epilogue was written by TobyAndMavisForever where Diesel headed to the Little Western branch to pass his apologies over to Duck. This is shown in the Sodor: The Modern Years episode Endgame.
- Galloping Sausage, Post and Prejudice and Worked Out are referenced.
- WildNorWester as Thomas, Edward, Henry, Gordon, James, Percy, Toby, Duck, Diesel, The Fat Controller, D261, Bear, the Troublesome Trucks, The Spiteful Brake Van and the British Railways Controller
- ANB as Alice