Duck and the Slip Coaches is a season 18 episode.
Plot
Recently, the railway has not been doing a good job on being on time and the odds are stacked up against Sodor during the summer when visitors like to come. Duck tells the other engines about slip coaches, coaches that can be uncoupled while the train is moving. But James takes all the credit for the idea, much to Duck's dismay. However, Duck gets the last laugh when James gets into an incident with the coaches leading Sir Topham Hatt to allow Duck to pull the coaches.