Thomas and friends work together to restore an old castle and find a missing friend, Stephen - the Real Life locomotive Stephenson's Rocket with an added face.
King of the Railway contains examples of:
- Animation Bump: The animation as of this special is much more fluid, due to the show being animated by Arc. As a result, the sky is bluer, the trains' smoke is more detailed, and better camera angles are used. The trains' facial expressions are also more exaggerated, making a wider range of emotions.
- Art Shift: The introduction to the now ruined Ulfstead Castle has medieval-themed illustrations to tell the events that happened to it.
- The Big Race: Caitlin and Connor have one along with Gordon and Spencer at the end of the movie.
- Brick Joke: The suit of armor that Percy spots throughout the movie. Near the end, Norramby wears it.
- The Bus Came Back: Jack the Front Loader makes his first appearance since the series went CGI. He would end up being the first of many old characters brought back by the new showrunners.
- Cannot Keep a Secret: Thomas can't resist telling a downbeat Stephen about his special job, pivoting the chain of events.
- Creative Closing Credits: The credits play over a montage of scenes from the movie, accompanied by "It's Gonna Be a Great Day".
- Earn Your Happy Ending: After tons of effort to restore the Ulfstead castle and Stephen trying and failing to find a new job in Sodor, the work is completed, Stephen finally gets a job working Sir Robert Norramby's estate and King Godred's crown is finally found.
- Freudian Trio: Thomas, James, and Percy end up forming one in this movie.
- Historical Longevity Joke: When the engines first meet Stephen, Percy asks him if he ever saw real knights in shining armor. Stephen tells Percy that he hasn't, as he may be old, but he's not that old. He then tells him "And before you ask, I never saw dinosaurs, either."
- Musical Chores: "Working Together Again", where James, Thomas, and Percy haul a huge load Henry was supposed to take to Ulfstead Castle.
- One-Steve Limit: Stephen shares the name of Sir Topham Hatt's grandson.
- Random Events Plot: The movie ricochets back and forth between Gordon and Spencer's rivalry, the arrival of Stephen, and the search for King Godred's crown. These all tie back into the restoration of Ulfstead Castle.
- Take That!: The issue of Henry's coal. For context, during seasons 10 through 16, it was said Henry still needed special coal, even though his new shape was meant to remedy this. Oftentimes, this special coal need was nothing more than convenient plot device, and in some cases, the writing made it sound like a G-Rated Drug, when it really wasn't. The following line was put in by Brenner to put the issue to bed once and for all:Toby: Henry's broken down!
Gordon: Don't tell me he needs Special Coal again...
Toby: No, Gordon. That was fixed years ago! - Wham Episode: Ulfstead Castle is restored, and Stephen found King Godred's crown.
