Series 18

The eighteenth season of the television series began airing on 25 August 2014 in the UK and on 4 November 2014 in the US. It contained twenty-six episodes. Like the seventeenth season, six episodes were released on DVD in the US before airing on television. It concluded in the UK on 31 July 2015.

Songs

 * It's Christmas Time
 * The Best Friends Express

Characters

 * Thomas
 * Edward
 * Henry
 * Gordon
 * James
 * Percy
 * Toby
 * Duck
 * Oliver
 * Bill and Ben
 * Harvey
 * Emily
 * Spencer
 * Stanley
 * Hiro
 * Charlie
 * Scruff
 * Stephen
 * Connor
 * Caitlin
 * Porter
 * Gator
 * Timothy
 * Diesel
 * Mavis
 * Salty
 * Den
 * Dart
 * Paxton
 * Sidney
 * Stafford
 * Marion
 * Skarloey
 * Rheneas
 * Peter Sam
 * Duncan
 * Victor
 * Luke
 * Millie
 * Rusty
 * Annie and Clarabel
 * Henrietta
 * Toad
 * Rocky
 * Bertie
 * Cranky
 * Captain
 * Owen
 * Reg
 * Sir Topham Hatt
 * Sir Robert Norramby
 * Mr. Percival
 * Dowager Hatt
 * Father Christmas
 * The Wellsworth Stationmaster
 * Gator's Driver
 * Thomas' Guard
 * The Teacher
 * The Blond-haired Boy
 * The Schoolchildren
 * The Groundsman
 * The Dock Manager
 * The Welsh Bird Watcher
 * The Lady with the Big Hat
 * Some Workmen
 * Whiff (does not speak)
 * Belle (does not speak)
 * Harold (does not speak)
 * Kevin (does not speak)
 * The Duchess of Boxford (does not speak)
 * Rosie (cameo)
 * Ferdinand (cameo)
 * 'Arry and Bert (cameo)
 * Norman (cameo)
 * Sir Handel (cameo)
 * Winston (cameo)
 * Merrick (cameo)
 * Farmer McColl (cameo)
 * The Dairy Manager (cameo)
 * The Bird Watcher (cameo)
 * The Ginger-haired Boy (cameo)
 * The Grumpy Passenger
 * The Great Railway Show Judge (cameo)
 * Flynn (mentioned)
 * Queen Elizabeth II (mentioned)
 * Sodor United Football Team (mentioned)
 * Alicia Botti (not named; mentioned)
 * Bash (learning segment)

Characters Introduced

 * Samson
 * Slip Coaches
 * The Deputy Minister
 * The Postman

Half hour format
When Season 17 aired on PBS in the US, each broadcast airs two episodes, a song & a Mr. Perkin's Railway segment and Guess Who? Puzzles segments. When they were broadcasted on Nick Jr., the segments are omitted.

Fast & Reliable

 * Old Reliable Edward
 * Song: On a Journey Today
 * Not So Slow Coaches

There’s Always a Good Explanation

 * Flatbeds Of Fear
 * Song: Searching Everywhere
 * Disappearing Diesels

Special Friends

 * Toad’s Adventure
 * Song: Hey, Hey Thomas!
 * Duck and the Slip Coaches

Please Be Patient

 * Thomas the Quarry Engine
 * Song: On a Journey Today
 * Duck in The Water

Signals & Alarms

 * Signals Crossed
 * Song: Hey, Hey Thomas
 * Thomas and the Emergency Cable

Going Underground

 * Marion and the Pipe
 * Song: Let's Be Brave
 * Missing Gator

Christmas Cheer!

 * Duncan The Humbug
 * Song: It's Christmas Time
 * The Perfect Gift

Passengers
Song: Working Together
 * Duncan and the Grumpy Passenger
 * Spencer’s VIP

Illuminating Minds

 * No Steam Without Coal
 * Song: Monsters Everywhere
 * Toad’s Bright Idea

Coming Home for Christmas

 * Last Train for Christmas
 * Song: It's Christmas Time
 * Long Lost Friend

Recycle Recycle Recycle!

 * Timothy and the Rainbow Car
 * Song: Let's Be Brave
 * Samson Sent for Scrap

Jurassic Sodor

 * Marion and the Dinosaurs
 * Song: Monsters Everywhere
 * Millie and the Volcano

Special Deliveries

 * Emily Saves the World
 * Song: Searching Everywhere
 * Samson at Your Service

UK and AUS

 * Mark Moraghan as the narrator
 * Ben Small as Thomas, Toby, Rheneas, the Troublesome Trucks and Owen
 * Keith Wickham as Edward, Henry, Gordon, James, Percy, Harvey, Salty, Den, Stafford, Skarloey, Bertie, Captain, Sir Topham Hatt, Mr. Percival, Dowager Hatt, the Wellsworth Stationmaster, Some Workmen, one of Sir Topham Hatt's Assistants, Some Passengers, Thomas' Guard, the Grumpy Passenger, Gator's Driver, the Steamworks Worker, the Groundsman, the Postman and the Bird Watcher
 * Teresa Gallagher as Emily, Mavis, Annie, Clarabel, the Teacher, the Blond-haired Boy, the Lady with the Big Hat, Station Speakers, Some Passengers and Some Children
 * Kerry Shale as Diesel
 * Steven Kynman as Duck, Porter, Paxton, Dart, Peter Sam and the third Slip Coach
 * Togo Igawa as Hiro
 * Michael Legge as Luke
 * Jonathan Forbes as Connor
 * Rebecca O'Mara as Caitlin and the second Slip Coach
 * Matt Wilkinson as Stanley, Spencer, Charlie, Scruff, Rusty, Rocky, Cranky, the Dock Manager, Some Workman and the Man with the Hat
 * Miranda Raison as Millie and the Knapford station speaker
 * Jonathan Broadbent as Bill, Ben and the first Slip Coach
 * Clive Mantle as Gator
 * Maggie Ollerenshaw as Henrietta
 * Olivia Colman as Marion
 * Bob Golding as Stephen and Sidney
 * Tim Whitnall as Timothy, Reg and the Deputy Minister
 * Joe Mills as Oliver, Toad and the Welsh Bird Watcher
 * Tom Stourton as Duncan
 * David Bedella as Victor
 * Robert Wilfort as Samson
 * Mike Grady as Sir Robert Norramby

US and CAN

 * Mark Moraghan as the narrator
 * Martin Sherman as Thomas, Percy and Diesel
 * William Hope as Edward, Toby, Rocky and the Dock Manager
 * Kerry Shale as Henry, Gordon, James, Scruff, Sir Topham Hatt, Mr. Percival, Some Passengers and Some Workmen
 * Keith Wickham as Harvey, Salty, Den, Stafford, Skarloey, Bertie, Captain, Dowager Hatt, the Wellsworth Stationmaster, Some Passengers, Thomas' Guard, the Grumpy Passenger, the Groundsman, the Postman and the Bird Watcher
 * Teresa Gallagher as Mavis, Annie, Clarabel, the Teacher, the Lady with the Big Hat, Station Speakers, Some Passengers and Some Children
 * Jules de Jongh as Emily, The Blond-haired Boy, Some Passengers and Some Children
 * Steven Kynman as Duck, Paxton, Dart, Peter Sam and the third Slip Coach
 * Jonathan Forbes as Connor
 * Rebecca O'Mara as Caitlin and the second Slip Coach
 * Togo Igawa as Hiro
 * Ben Small as Charlie, Stanley, Rheneas, the Troublesome Trucks and Owen
 * Michael Legge as Luke
 * Miranda Raison as Millie and the Knapford Station Speaker
 * Jonathan Broadbent as Bill, Ben and the first Slip Coach
 * Bob Golding as Stephen and Sidney
 * David Menkin as Porter and Stanley
 * Glenn Wrage as Spencer, Cranky, one of Sir Topham Hatt's Assistants, Gator's Driver and the Steamworks Worker
 * Matt Wilkinson as Rusty, Some Passengers and some Workmen
 * Olivia Colman as Marion
 * Maggie Ollerenshaw as Henrietta
 * Clive Mantle as Gator
 * Tim Whitnall as Timothy, Reg, the Deputy Minister and the Man with the Hat
 * Joe Mills as Oliver, Toad and the Welsh Bird Watcher
 * Tom Stourton as Duncan
 * David Bedella as Victor
 * Robert Wilfort as Samson
 * Mike Grady as Sir Robert Norramby

Trivia

 * The final six episodes of this season were sold to PBS, Milkshake and the ABC as part of the Season 19 block, despite being produced with Season 18.
 * This season marks the first of a few things:
 * Oliver, Toad and Duncan's first appearances in full CGI.
 * Crovan's Gate, Sodor Castle, Rheneas Viaduct, the Woodland Way, and Glennock's first appearance in full CGI.
 * Henrietta gains a face for the first time in the television series.
 * The first season to have an episode set during the events of the season's special.
 * The first season to have Tim Whitnall, Olivia Colman, Clive Mantle, Maggie Ollerenshaw, Joe Mills, Tom Stourton and Robert Wilfort as part of the voice cast.
 * The first season since its introduction where the Sodor Search and Rescue Centre does not appear, although it was mentioned in Millie and the Volcano.
 * The first season in which Flynn doesn't appear since his introduction in Day of the Diesels, although he was mentioned in Millie and the Volcano.
 * The first season since their debuts where Whiff and Kevin appear, but don't speak.
 * The first season where the Duchess of Boxford appears, without the Duke of Boxford.
 * This season marked the last of a few things:
 * The last season to have Ben Small and Martin Sherman as part of the voice cast.
 * John Hasler and Joseph May took over the role of Thomas for their respective dubs in The Adventure Begins. Hasler also took over the role of Rheneas in both dubs.
 * Christopher Ragland took over the role of Percy in the US and the Troublesome Trucks in both dubs.
 * Rob Rackstraw took over the role of Toby in the UK, Stanley in the US and Flynn in both dubs.
 * Kerry Shale took over the role of Diesel in the US.
 * Steven Kynman took the role of Charlie in the US.
 * To date, it is currently unknown who will voice Ferdinand in the UK dub and Owen in both dubs.
 * The last season to have an episode written by Paul Larson and Laura Beaumont.
 * The last season to have Keith Wickham as the voice of Percy in the UK dub. Nigel Pilkington takes over the role starting with the nineteenth season.
 * The last season to have Sir Topham Hatt and James voiced by Kerry Shale in the US. Keith Wickham and Rob Rackstraw took over the respective roles beginning in The Adventure Begins.
 * The final season the New Series intro and credits are used. This is also the final season with the original rendition of the Engine Roll Call. Despite this, a few latest DVD releases which contained the nineteenth season (with some sixteenth or eighteenth season) episodes retain these. When the six episodes from Dinos and Discoveries aired on PBS Kids in May 2016, it used the nineteenth season  opening,  Engine Rollcall, and ending.
 * Like the seventeenth season, although Arc Productions had officially taken over the animation aspects of the television series, the episodes still used the opening titles and closing credits made by Nitrogen Studios. This was the final season to use their opening and closing footage and from the nineteenth season, the opening and closing footage was made by Arc Productions.
 * According to Ryan Hagan of SiF, the episodes in Spills and Thrills were going to be part of this season.