Air date: September 5th, 2016 (UK)
One day, Sidney is taking a train of empty trucks to the Blue Mountain Quarry, when he comes across Percy being placed on a flatbed after having an accident. Percy tells Sidney that he damaged his wheels in the crash and tries to remind him about the time he damaged his own wheels, but Sidney does not remember this. He then leaves to take his trucks to the quarry, but goes the wrong way.
A few days later, Sidney is at Knapford Station, when the Fat Controller arrives. He tells Sidney that Percy's new wheels have arrived, and he wants him to go to the Docks and bring them to the Steamworks. Sidney fears that he will forget about his job, so Thomas suggests that he sing a song to remind him about it. Sidney likes the idea, and begins singing a little song to himself as he leaves the station.
Sidney arrives at Wellsworth Station, where Gordon is waiting with the express. Sidney tells Gordon about his special job, but Gordon laughs at him and leaves. Sidney sets off down the line, but as he does, he forgets what his song was, as well as his job. After some thinking, he comes to the conclusion that he had to pick up an old boiler from the rubbish dump, and sets off at once.
At the dump, Whiff is shunting trucks of rubbish, when Sidney arrives. Sidney tells Whiff about his job, but Whiff tells him that the rubbish dump has no boilers. He tells Sidney that elephants never forget anything, which makes Sidney believe that he has to pick up an elephant from the Animal Park. He leaves the rubbish dump and arrives at the Animal Park, but finds no elephants.
Sidney returns to Knapford, where he finds a group of passengers complaining about their train being late. Sidney believes that this is his special job, and takes the passengers to Brendam Docks. When he arrives, he finds the Fat Controller waiting for him, and the Fat Controller reminds him about Percy and his new set of wheels. Sidney takes the new wheels to the Steamworks, cheerfully singing along the way.
By the time Sidney arrives at the Steamworks, it is already evening. When Percy asks him about his whereabouts, Sidney does not remember, but tells Percy that he has brought his new wheels and asks Percy if he thought he would have forgot. The two engines laugh together.
This episode contains examples of:
- Alliterative Title: Sidney Sings.
- A Day in the Limelight: This is Sidney's first focus episode.
- Call-Back: Percy damages his wheels and reminds Sidney of the time he damaged his wheels, while Sidney wants to collect Percy's new wheels just as he had done for him.
- Elephants Never Forget: After Sidney starts forgetting things, Whiff tells him that elephants never forget anything, which makes Sidney believe that he has to pick up an elephant from the Animal Park.
- Everyone Laughs Ending: Sidney and Percy joke about Sidney's wheels for a laugh at the end.
- Flashback Cut: The start of the episode shows the time Sidney hanging from the ceiling and Percy rescuing him from "The Missing Christmas Tree Decorations". Also counts as Flashback with the Other Darrin, as both dubs' actors for Percy had changed since then.
- Flashback with the Other Darrin: During the flashback from "The Missing Christmas Tree Decorations", Percy's voice is redubbed with his current voice actors for their respective regions. The Japanese dub does this with Sidney's voice.
- Forgetful Jones: Sidney forgets what he's supposed to be doing every time he stops to have a conversation.
