Thomas and the Special Letter is the twenty-second episode of the fourth series and the 100th episode of the television series overall. It is based on the story "The Fat Controller's Engines" from The Railway Series book, The Eight Famous Engines.
After taking his last train of the day, Thomas meets up with Percy and Toby and it turns out that all three engines have been asked to report to the big station after the day's work is done. Thomas thinks something is happening and is surprised to see BoCo, Mavis, Donald, Douglas, Bill, Ben and Oliver all travel past, also heading for the station; Thomas, Percy and Toby are now very curious and follow the others.
At Tidmouth Sheds, the Fat Controller silences his engines whistling excitedly to tell them he recently received a letter from a five-year-old girl who lives in the big city. She writes that she and her friends would like to meet Thomas and his friends and invites him to their local station. The Fat Controller tells the engines that a lot of children would like to meet them so they will give them the chance and the first eight are going to travel to the big city. The Fat Controller's engines blow their whistles excitedly again, prompting the Fat Controller to command silence again. While the eight engines are gone, the rest will all be running the line and asks to show them what to do.
Oliver is due to take charge of Thomas' Branch Line and Thomas shows him what to do using some coaches (as Annie and Clarabel will be going with Thomas to the city). Thomas is getting more and more excited and boasts about his race with Bertie, but when he tries to show off, he accidentally crashes through some buffers and a fence, rolls down a hill and smashes through a brick wall. No one is hurt, but Thomas' front end is badly bent from the impact. The Fat Controller is called and sends some workmen to repair Thomas but warns them that if they do not get finished in time, they will have to go to the city without him. Thomas is very sad and worried that he will miss out on the trip.
The next day at 8:00 AM, the engines are ready to leave (with Percy and Toby travelling on flatbeds) but there is no sign of Thomas yet. The Fat Controller agrees to wait one more minute for Thomas before they must leave. Now repaired, Thomas arrives just in time and the cavalcade of engines leave for their trip to the city. After having arrived at the city safely, the engines are lined up in a wonderful shed where many children come to meet them. Thomas tells Percy how glad he is that the little girl wrote to the Fat Controller, citing that happiness is what brings in response to a letter.
- Donald and Douglas
- Bill and Ben
- Annie and Clarabel
- Sir Topham Hatt
- Henrietta (Cameo)
- The Vicar of Wellsworth (Cameo)
- Refreshment Lady (Cameo)
- Tom Tipper (Cameo)
- The Crovan's Gate Policeman (Cameo)
- One Little Boy (Cameo)
- The Elephant Keeper (Cameo)
- One Member of the Railway Society (Cameo)
- The Ffarquhar Stationmaster's Wife (Cameo)
- Duke (portrait; cameo)
- Stepney (behind the scenes; cameo)
- Bertie (Mentioned)
- Daisy (dropped)
- Island of Sodor
- The Big City
- The Big Airy Shed
- The closing scene is featured on the 1998-2005 ABC for Kids promo.
- Going by production order, this is the twenty-first episode of the fourth series.
- At the sheds, the audio of the engines whistling was reused from the second series episode, The Deputation.
- This episode marks Donald's last speaking role and the last time he appears with Douglas until the sixth series episode, Twin Trouble, as well as the last time they have Scottish accents in the US dub until the seventh series episode, Bad Day at Castle Loch.
- Behind the scenes footage for this episode was filmed for the 1995 documentary The Thomas the Tank Engine Man and it was revealed by David Mitton on the set that the engines were still heading to London like in the book that this episode originated from.
- A reference to the first series episode, Thomas and Bertie is made in this episode.
- The picture of Duke from the fourth series episode, Bulldog can be seen in Sir Topham Hatt's office.
- According to a post on Britt Allcroft's Facebook page, this episode partially inspired the film, Thomas and the Magic Railroad.
- In the Behind the Scenes footage, it shows Donald passing by Thomas, Percy and Toby, but for unknown reasons, he was replaced by Douglas. The narrator even calls Douglas "Donald" in the actual episode. Additionally, Stepney can be seen in the Big City shed.
- The Mainland is referred to as "The Big City" in this episode; this also marks the first, albeit brief, appearance of the Mainland in the television series.
- This is the first episode where the North Western Railway engines numbered 1-11 have appeared and/or spoken all together in an episode. Additionally, this was the only time until the special, Sodor's Legend of the Lost Treasure to do so.
- Despite their appearances in the episode, Edward and Duck do not appear in the nameboard sequence at the end of the episode in the Japanese dub.
- Thomas' accident is similar to a crash when an LB&SCR E4 0-6-2T tank engine No. 32493 also crashed into a wall, but the tank engine ran off from the turntable and crashed into the wall at Southern Region sheds.
- This episode marks the only appearance of Bill and Ben in the fourth series.
- This is the only episode in the US version that George Carlin refers a "freight car" as a "truck." However, this is the first time in the US version that the term, "truck" is said in the US version.
- The three berth garage from TUGS appears at Tidmouth sheds.
- The events of this episode are mentioned by Thomas in the special, The Great Race and Gordon in the special, Big World! Big Adventures! during the song, Where in the World is Thomas?
- Nearly all the engines on the North Western Railway introduced so far are together in this episode, except for Daisy. This is due to Daisy and BoCo sharing the same chassis.
- Douglas was actually the one who spoke when the narrator said that Donald spoke.
- In Toby's third close-up, his face is loose.
- In the close-up of Thomas' driver, Thomas appears to be pulling a red coach instead of Annie.
- In the Dutch dub, the audio is out of sync.
- When Thomas and Percy first leave Elsbridge, Toby is not in his siding, but Henrietta is still there and his bell can be heard. In addition, they went the opposite way when they went to the station, rather than follow the other engines.
- In the close-ups of the Fat Controller giving the announcement, Duck's funnel is a different shape and his face is missing.
- As Henry leaves Elsbridge, one of his bogie wheels is loose.
- In the Big City shed, Percy's cab roof is lifted slightly.
- When Thomas went through the buffers, rails were seen on the ground, showing how he moved straight.
- During the panning shot of the engines when the Fat Controller reads the little girl's letter, James and Gordon's eyes are wonky.
- When Thomas starts talking to Oliver, some of the steam from his funnel disappears, indicating a film cut.
- When James leaves Elsbridge, his eyes are wonky.
- When Oliver passes through Elsbridge with Donald, he has Ben's whistle sound.
- In the close-up of Thomas at Tidmouth Sheds, Percy's right lamp iron is bent.
- In the shot of Thomas going down the embankment, he is seen going through the fence again, only it is already broken in that shot.
- Henry's lamp is not on the lamp iron.
- The overhead shot of the engines in the Big City shed appears to be mirrored, as indicated by the fact that Thomas, Henry and Duck's lamps are on the wrong sides of their fronts and that Toby's bell is on the wrong side of his roof.
- All of the engines' eyes are wonky in the horizontal scan of Tidmouth Sheds.
- In the UK version, when the Fat Controller shouts "Silence!" he sounds severely muffled both times. In the US dub, he sounds clear.
- When Douglas passes through Elsbridge, he is missing his brake pipe.
- In the US dub, the flatbeds were referred to as trucks.
- Thomas looks happy when he crashes through some buffers.
- In the Danish dub, when Thomas and Oliver are shunting coaches, the narrator mistakes Oliver for Percy.