|Screenshot||UK title (top)|
US title (bottom)
|Episode number #|
|"Thomas and the Billboard"||1st September 2008||#01|
|Thomas shows a famous storyteller around, but keeps making detours to help the others.|
|"Steady Eddie"||2nd September 2008||#02|
|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"
|3rd September 2008||#03|
|Rosie and Emily are pulling a train for a fair, but Rosie wants to pull it alone.|
|"Mountain Marvel"||4th September 2008||#04|
|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"||5th September 2008||#05|
|Henry worries that the workmen are going to cut down the wishing tree.|
|"Heave Ho Thomas!"||8th September 2008||#06|
|A large new engine called Hank arrives, but Thomas is determined not to need his help.|
|"Toby's Special Surprise"||9th September 2008||#07|
|Toby wants to make an impression by searching Sodor for something special.|
|"Excellent Emily"||10th September 2007||#08|
|Emily becomes arrogant after receiving praise from the Fat Controller.|
|"The Party Surprise"||11th September 2008||#09|
|Freddie decides to reorganise a winter party from Mr. Percival's house to the Wharf as a surprise for Colin the crane.|
|"Saved You!"||12th September 2008||#10|
|Thomas wants to prove his heroism when he learns a fireman is to be honoured.|
|"Duncan and the Hot Air Balloon"||15th September 2008||#11|
|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"||16th September 2008||#12|
|When James ignores Hector's advice, he gets caught in bad winter weather.|
|"Tram Trouble"||17th September 2008||#13|
|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"||18th September 2008||#14|
|Thomas and Diesel race backwards.|
|"Gordon Takes a Shortcut"||19th September 2008||#15|
|Gordon gets lost while taking a shortcut and refuses to ask for help.|
|"The Man in the Hills"||22nd September 2008||#16|
|Thomas and the narrow gauge engines collect presents for Mr. Percival's birthday.|
|"Thomas Puts the Brakes On"||23rd September 2008||#17|
|Thomas' brakes malfunction while delivering bricks to repair a bridge.|
|"Percy and the Bandstand"||24th September 2008||#18|
|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"||25th September 2008||#19|
|Skarloey refuses Rheneas' help to pull a train for a puppet show and ends up playing the trucks' games.|
|"Best Friends"||26th September 2008||#20|
|Thomas tries to avoid telling Percy he has been given a job Percy wants to do.|
- Engine Rollcall (CGI face version)
- 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 version)
- 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)
- Bulgy (cameo)
- Max or Monty (cameo)
- Farmer Trotter (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. 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 Breaks 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 Destintions
- 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 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 since their debuts where Rocky and Cranky appear, but don't 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 TV 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 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 TV, 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.
- This season contained the 300th episode of the television series.
- Pierce Brosnan was originally going to narrate this season, but was later replaced by Michael Angelis and Michael Brandon for unknown reasons.
- In the UK, this season was supposed to be show 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 utilize a CGI face mask. However, two pictures from a magazine story show Harvey with a CGI face.
- The series cost £2.5 million to make, with each episode taking around five days to film.