|Screenshot||UK title (top)|
US title (bottom)
|Written by||Original UK|
|Episode number #|
|"Thomas and the Billboard"||Mark Robertson||1st September 2008|| #01 UK
|When a photographer comes to photograph the engines for a billboard Diesel accidentally obscures Thomas. Believing that Diesel did it on purpose, Thomas deliberately avoids him when he accidentally loses the billboard and has to get another arranged.|
|"Steady Eddie"||Sharon Miller||2nd September 2008|| #02 UK
|Edward takes the Great Waterton water wheel on the scenic route to show off to his friends.|
| "Rosie's Funfair Special"|
"Rosie's Carnival Special"
|Andrew Viner||3rd September 2008|| #03 UK
|Rosie and Emily are pulling a train for a fair, but Rosie wants to pull it alone.|
|"Mountain Marvel"||Sharon Miller||4th September 2008|| #04 UK
|Peter Sam rushes to finish his jobs in order to hear a tale about Proteus from the famous storyteller, Miss Marvel.|
|"Henry Gets it Wrong"||Abi Grant||5th September 2008|| #05 UK
|Henry worries that the workmen are going to cut down the wishing tree.|
|"Heave Ho Thomas!"||Sharon Miller||8th September 2008|| #06 UK
|A large new engine called Hank arrives, but Thomas is determined not to need his help.|
|"Toby's Special Surprise"||Sharon Miller||9th September 2008|| #07 UK
|Toby wants to make an impression by searching Sodor for something special.|
|"Excellent Emily"||Paul Larson||10th September 2008|| #08 UK
|Emily becomes arrogant after receiving praise from the Fat Controller.|
|"The Party Surprise"||Simon Spencer||11th September 2008|| #09 UK
|Freddie decides to reorganise a winter party from Mr. Percival's house to the Wharf as a surprise for Colin the crane.|
|"Saved You!"||Paul Larson||12th September 2008|| #10 UK
|Thomas wants to prove his heroism when he learns a fireman is to be honoured.|
|"Duncan and the Hot Air Balloon"||Mark Robertson||15th September 2008|| #11 UK
|Mr. Percival's twins are getting a ride in the Hot Air Balloon for their birthday, but Duncan wants to take them himself.|
|"James Works it Out"||Simon Spencer||16th September 2008|| #12 UK
|When James ignores Hector's advice, he gets caught in bad winter weather.|
|"Tram Trouble"||Sharon Miller||17th September 2008|| #13 UK
|Toby and Flora are heading a parade at Great Waterton; Thomas thinks Toby would rather lead the event on his own and tries to distract Flora.|
|"Don't Go Back"||Simon Spencer||18th September 2008|| #14 UK
|Thomas and Diesel race backwards.|
|"Gordon Takes a Shortcut"||Wayne Jackman||19th September 2008|| #15 UK
|Gordon gets lost while taking a shortcut and refuses to ask for help.|
|"The Man in the Hills"||Sharon Miller||22nd September 2008|| #16 UK
|Thomas and the narrow gauge engines collect presents for Mr. Percival's birthday.|
|"Thomas Puts the Brakes On"||Mark Robertson||23rd September 2008|| #17 UK
|Thomas' brakes malfunction while delivering bricks to repair a bridge.|
|"Percy and the Bandstand"||Paul Larson||24th September 2008|| #18 UK
|Percy is tasked with bringing Lady Hatt to a surprise party - but the unknowing Lady Hatt tells him to go elsewhere.|
|"Push Me, Pull You"||Sharon Miller||25th September 2008|| #19 UK
|Skarloey refuses Rheneas' help to pull a train for a puppet show and ends up playing the trucks' games.|
|"Best Friends"||Anna Starkey||26th September 2008|| #20 UK
|Thomas tries to avoid telling Percy he has been given a job Percy wants to do.|
- Donald and Douglas
- Sir Handel
- Peter Sam
- Mighty Mac
- Sir Topham Hatt
- Lady Hatt
- Dusty Miller
- The Photographer
- The Engineer
- The Dairy Manager
- Stepney (does not speak in UK dub)
- Harvey (does not speak)
- Arthur (does not speak)
- 'Arry and Bert (do not speak)
- Annie and Clarabel (do not speak)
- Henrietta (does not speak)
- Rocky (does not speak)
- Trevor (does not speak)
- Alfie (does not speak)
- Cranky (does not speak)
- Jeremy (does not speak)
- Dowager Hatt (does not speak)
- Mrs. Percival (does not speak)
- Jenny Packard (does not speak)
- Sodor Brass Band (does not speak)
- Farmer Trotter (does not speak)
- Bulgy (cameo)
- Max or Monty (cameo)
- Proteus (mentioned, seen as a statue)
- The Mayor of Sodor (mentioned)
- Dennis (learning segment)
- The Balloon Repairman
- The Bargeman
- The Tree Specialists (do not speak)
- Mr. Giggles (does not speak)
- Miss Marvel (does not speak)
- The Fireman (does not speak)
- The Percival Children (The Percival Twins; do not speak: The rest of them; cameo)
- The Ginger-haired Boy (cameo)
- The Blond-haired Boy (cameo)
- The Teacher (cameo)
Half hour format
When season 12 aired on PBS Kids, Nick Jr. UK and Treehouse, each broadcast had 2 episodes from season 12, a segment dedicated to one of Thomas' friends and past animated learning segments and songs from seasons 8, 9 and 10 were used.
- Best Friends
- Learning Segment: Dot to Dot - Emily
- Song: H is for Harold
- Thomas' Favourite Friends - Rosie and Molly
- Learning Segment: What is Henry Thinking of?
- Henry Gets it Wrong
- Thomas and the Billboard
- Learning Segment: Guess the Engine - Percy
- Learning Segment: Who Should Take the Telegraph Pole?
- Thomas' Favourite Friends - Toby
- Learning Segment: Which Way Should Thomas and Emily Go?
- Learning Segment: Which Whistle Suits Thomas?
- Steady Eddie
- Heave Ho Thomas!
- Learning Segment: Guess the Engine - James
- Song: Pride
- Thomas' Favourite Friends - Henry
- Learning Segment: Which Engine for Which Job?
- Toby's Special Surprise
- Don't Go Back
- Learning Segment: Dot to Dot - Gordon
- Learning Segment: Over the Bridge
- Thomas' Favourite Friends - Gordon
- Learning Segment: Which Track for Henry?
- Learning Segment: Emily Huffs out of the Station
- Percy and the Bandstand
- Thomas Puts the Brakes On
- Learning Segment: Guess the Engine - Emily
- Song: Brave
- Thomas' Favourite Friends - Neville and Dennis
- Learning Segment: Getting There
- Gordon Takes a Shortcut
Presents and Prizes
- The Man in the Hills
- Learning Segment: Dot to Dot - Edward
- Learning Segment: What is Thomas Thinking of?
- Thomas' Favourite Friends - Harold and Jeremy
- Learning Segment: Which Load to Which Station?
- Excellent Emily
- Tram Trouble
- Learning Segment: Dot to Dot - Toby
- Song: Responsibility
- Thomas' Favourite Friends - Edward
- Learning Segment: Who Can get to the Washdown?
- James Works it Out
- Rosie's Funfair Special
- Learning Segment: Dot to Dot - Percy
- Song: Togetherness
- Thomas' Favourite Friends - Diesel
- Learning Segment: Which Load for What Occasion
- Push Me, Pull You
- Duncan and the Hot Air Balloon
- Learning Segment: Dot to Dot - Thomas
- Learning Segment: What Does Toby see?
- Thomas' Favourite Friends - The Narrow Gauge Engines
- Learning Segment: Percy's Treasure
- Mountain Marvel
- Saved You!
- Learning Segment: Dot to Dot - Gordon
- Song: Doing it Right
- Thomas' Favourite Friends - Percy
- Learning Segment: Surprise Destinations
- The Party Surprise
- This was the first season of several things:
- The first season of the CGI Series.
- The first season where all engines' faces, human characters, animals and environmental surroundings are in full CGI and move.
- Harold, Sir Topham Hatt, Lady Hatt, Alice, The Engineer, Dowager Hatt, Jenny Packard and Sodor Brass Band's first appearances in full CGI.
- Sharon Miller's first season as head writer.
- The first season to have twenty episodes.
- The first season produced and to contain CGI by Nitrogen Studios.
- The first HiT season recorded and edited in 25fps (aside from the end credits).
- The first Thomas & Friends production since Thomas and the Magic Railroad to have moving people.
- The first season to premiere on Milkshake! before the half hour airings on Nick Jr. in the UK.
- The first season since their debuts where Rocky and Cranky appear, but do not speak in any of their appearances.
- This was also the last season of several things as well:
- The last season to use models and clay faces, however the clay faces were only used in background shots.
- Simon Spencer's last season as producer.
- The last season filmed at Shepperton Studios.
- The last season to feature songs by Ed Welch.
- The television series veteran Steve Asquith's final season as director.
- The last season to have all of the characters voiced by the narrator until Thomas Goes to New York.
- The last time Paul Larson writes an episode until the seventeenth season as well as the last season where he writes an episode by himself.
- The final time until the eighteenth season episode, Samson Sent for Scrap to use the brake sound from The Train.
- This was the last season to have songs sung by children until The Adventure Begins.
- The last season to open with Awdry's letter to Christopher in television broadcasts.
- This was also the only season of several things as well:
- The only season to use a hybrid model-CGI mix.
- Dino Athanassiou's only season as CGI director.
- Pete Atkin's only season as voice director.
- The only season where Ben appears without Bill.
- The only season not shown on Japanese television, but some episodes have been shown exclusively at Thomas Land's 3D Theatre and Video on Demand in Japan.
- The only CGI season not to have a full voice cast for the characters.
- Aside from the Teacher and the tree specialists, all of the characters introduced in this season have only ever appeared in their debut episodes.
- The only season not dubbed in Dutch.
- The only CGI season to have the characters talking to their selves, but their mouth is not moving.
- This season contained the 300th episode of the television series.
- Pierce Brosnan was originally going to narrate this season, but he was withdrawn from the series and Michael Angelis and Michael Brandon returned to replace Pierce Brosnan for the twelfth season to the sixteenth until Mark Moraghan took over them for the seventeenth season and King of the Railway.
- In the UK, this season was supposed to be shown after The Great Discovery, but was brought forwards for unknown reasons.
- This season was never shown in Hungary, Norway, Romania, Poland and the Netherlands.
- Harvey and Arthur were the only engines not to utilise a CGI face mask. However, two pictures from a magazine story show Harvey with a CGI face.
- The series cost £2.5 million/$3,126,750.00 to make, with each episode taking around five days to film.