Koko Pulls It Off - S1.E24

The trainees are taking their passenger test. If they pass, they'll be able to carry passengers all on their own. Brewster and Wilson are a little nervous, but Koko is confident - after all, she's a passenger train! Mr. Simkins, from the Ministry of Chuggers, arrives to examine them. His 'jiggleometer' will tell him whether or not the trainees are riding smoothly. Koko volunteers to go first. Unfortunately, just as she starts, Simkins coughs and sets the machine off with a deafening beep. Koko jumps and Simkins gets thrown across the carriage. He fails Koko and, despite her protests to be given a second chance, is unmoveable. Broken-hearted, Koko goes off to the recycling yard and pours her heart out to Irving. Irving remembers Simkins of old and intervenes - reminding him of a similar situation in his own past. Simkins relents and gives Koko another chance! This time, without the jiggleometer, Koko passes with flying colours!