- “I've never been on a billboard before!”
Thomas and the Billboard is the first episode of the twelfth series.
It is Knapford Station's birthday and all of the engines are preparing for the festivities. A photographer comes to take a photo of the engines to put up a billboard at Knapford. Thomas is proudest of all; he has never been shown on a billboard before. To fit all of the engines into the photo, the photographer asks James to move back, Percy to move forward and tells Diesel to move forward, but Diesel accidentally obscures Thomas. However, no-one is aware of this.
Later, Thomas puffs into Maron to collect the billboard to bring to Knapford and is very upset to find that he is out of the photograph. Thomas thinks Diesel obscured him on purpose. He is so distracted that he barely notices a cow up ahead. He swerves into a siding at the last minute and knocks the billboard into a nearby river. Thomas goes back to Maron to explain what had happened. The photo's results were not correct anyway, so the photographer does not mind and tells Thomas to collect the engines again. Thomas is about to go when he sees Diesel approaching. Thomas refuses to tell Diesel about the new photo as he does not want Diesel to spoil this photo too.
Soon, all of the engines are back at the sheds, except Diesel. Gordon, Emily and James are worried as they have jobs to do, but Thomas is sure that he will be quick to fetch the photographer. On the way to Maron, Thomas sees Diesel, who is heading straight for the sheds. Thomas is worried, as Diesel will find out about the photo, so he takes a branch line back to Tidmouth. The engines get very cross when Thomas tells them to come back later, not knowing that it was just an excuse so Diesel would not see them. They have soon left, just as Diesel rolls past.
Later, the engines are back at the sheds, and Thomas puffs back to Maron to fetch the photographer. As the photographer climbs into Thomas' cab, Thomas sees Diesel coming. Worried that Diesel will see the photographer, he wheeshes a lot of steam to cover up the station, and Diesel rolls past, but the camera is now wet. The photographer has to let the camera dry, so Thomas tells the engines to come back later.
Soon, the engines all come back, but they still have not done their jobs. As the photographer is getting ready, nobody, except Thomas, notices that Diesel is not there. Just then, Diesel, who is doing the others' jobs, runs around the bend, to find all of the engines, ready to take the photograph for the new billboard. He stops so suddenly that the bunting falls off one of his trucks. Diesel is cross, as nobody had told him about it. The photographer is confused as he had told Thomas to tell everybody, including Diesel. All of the engines look at Thomas knowing that he is the culprit, making him feel terrible. Just then, Sir Topham Hatt arrives, and starts telling off Gordon, James and Emily for being not arriving for their work and explains that Diesel has had to do their jobs, and because of that, he is now late with his own work.
This makes Thomas feel even worse, and owns up that he did not tell Diesel about the photograph because Diesel had obscured him earlier, which he believes was on purpose. Diesel objects that the photographer had told him to move. The photographer realises what he did and explains that Diesel might have rolled too far. Thomas knew then he had made a mistake, he apologises to Diesel for accusing him and Sir Topham Hatt for all the trouble. Everything is soon rectified and the engines line up to take the photo, this time with Diesel not covering up Thomas. After the photo is taken, Thomas agrees to do Diesel's work, while Diesel takes the new billboard to Knapford.
That evening, Diesel picks up the new billboard and takes it to the festivities at Knapford. The party is a great success as Thomas and Diesel agree that the new billboard at Knapford is the best billboard they have ever seen.
- Sir Topham Hatt
- The Photographer
- Percy (does not speak)
- Sodor Brass Band (do not speak)
- Mr. Giggles (does not speak)
- Edward (cameo)
- Henry (cameo)
- Toby (cameo)
- Annie and Clarabel (cameo)
- Cyril the Fogman (cameo)
- The Ginger-haired Boy (cameo)
- The Schoolchildren (cameo)
- The Welsh Bird Watcher (cameo)
- Barrow Football Fan (cameo)
- The Female Puppet Show Entertainer (cameo)
- MC BUNN
- Tidmouth Sheds
- The Smelter's Yard
- The Works
- Brendam Docks (mentioned)
- Wellsworth (mentioned)
- Sodor Airport (mentioned)
- At the end of the episode, the brass band plays Thomas' theme (in time with the incidental music).
- This was originally supposed to be the first episode narrated by Pierce Brosnan in both English dubs, but for unknown reasons on why he left after The Great Discovery, Michael Angelis and Michael Brandon returned to the role of narrator in the UK and US, respectively.
- This episode marks the first of several things:
- Sharon Miller's first episode as head writer as well as the first episode to have a head writer.
- The first episode to feature animation from Nitrogen Studios.
- Nicole Stinn's first episode as a producer for Nitrogen Studios.
- Greg Tiernan's first episode as a director for Nitrogen Studios.
- Dino Athanassiou's first episode as animation director for Stardust Pictures.
- The first time since Thomas and the Magic Railroad that CGI animation was used.
- The first episode in 1080p progressive scan full HD.
- This episode marks the last of some things:
- Cyril the Fogman's last appearance until The Great Race and his last appearance in an episode until the twenty-second series episode, Samson and the Fireworks.
- This is the last episode where Edward, Henry, Gordon, James, Percy, Toby, and Emily are seen with their angry faces.
- This is the last episode where Edward is seen with his neutral face mask, Henry with his annoyed face mask, James with his confused face mask and Percy seen with his sad face mask.
- Henry has Gordon's face twice in this episode. This happens for the first time when he and Edward puff into Knapford at the beginning and then again at the celebration at the end.
- The narrator said that Diesel was puffing to Tidmouth, but he is a diesel engine.
- The narrator says that Thomas took a branch line back to Tidmouth Sheds. A branch line finishes at a dead end, and it is not a through route.
- When the narrator says that no one had noticed Diesel's absence, Gordon and Henry change places.
- When the engines came back to Tidmouth Sheds, Henry is next to Toby, but when Thomas tells the engines to come back later, Henry and Percy change places.
- When the CGI eyelids blink, they are sometimes partially transparent.
- When Gordon puffs by in the first scene, studio equipment is reflected in the coach windows.
- When Thomas apologises to Diesel, Diesel's face is smaller.