January 19th, 2015
The fourth season of Thomas' Sodor Adventures aired with Thomas and Algy on January 19th, 2015 to celebrate the one-year anniversary of the series. It finished airing on October 9th, 2015.
- Thomas and Algy - Thomas decides to race a bus named Algy, to prove to Bertie that engines are superior.
- Best Decorated Engine - Gordon inadvertently wins a "best decorated engine" competition.
- Triple Trouble - Bill, Ben and Charlie form a trio of pranksters and end up causing trouble.
- Duncan and Victor - When Duncan accidentally pushes Victor into a turntable well, Victor has to be repaired in his own Steamworks and Duncan ends up in charge.
- Timothy and Dennis - Timothy starts getting ridiculed by Dennis for being the only oil-burning standard gauge engine.
- Serious Samson - A new engine named Samson is heading towards Ulfstead Castle, but makes a mistake and instead, accidentally goes to Henry's Forest.
- Flora's Tram Coach - When Flora's tram coach is sent to the works to be repaired, she has to use regular branch line coaches, but doesn't feel confident.
- Brake Coaches - James thinks that he doesn't need brake coaches for a train, but is proven wrong when his brake coach breaks away on a hill.
- Stories of Digging - When Marion is asked to help Timothy at the Clay Pits, she instead tells stories about digging to Bill and Ben which causes confusion and delay.
- It's Not Easy Being Green - Gator has to take a goods train for Duck but ends up causing a mess.
- A Surprise for Bertram - A party is being set up on the Skarloey Railway, and the little engines need to look clean, but Bertram is too dirty to be in it, due to working at his old mine and it'll take a long time for him to be clean.
- Duke and Smudger's Past Adventures - Duke tells Peter Sam, Skarloey and Rusty the story of him and Smudger on the Mid Sodor Railway.
- Special Engines - Diesel tricks Stephen into doing his work, so that he can do Stephen's work of taking tourists around Ulfstead Castle.
- Neville at the Scrapyard - Neville is told to work at Crocks Scrap Yard, but is scared of Reg's "scrap sculptures".
- Dusty Rusty - Rusty's engine breaks, and he has to stay in the shed for several days until the new engine parts arrive from the Mainland.
- Duck and the Coaches - Duck is sad when Oliver is told to pull the Slip Coaches while he has to take a goods train to Arlesburgh.
- Cows and Whistles - A cow blocks Caitlin's line and it won't move, even when Caitlin uses her skirt, and due to this, causes the big engines to run late with their trains.
- Geoffrey's Overhaul - The Fat Controller lets Geoffrey go on an overhaul due to all the hard work he has done.
- The Wrong Sort of Coal - Samson gets in trouble with Thomas when he accidentally delivers American coal, which causes an outbreak of sickness on Sodor.
- Broken Down Crane - After lifting Murdoch, Rocky's cable snaps and Jerome and Judy have to take over his jobs.
- Yellow Rheneas - Rheneas has to be repainted yellow, but many engines confuse him with Duncan.
- Saved by the Belle - A fire rages near Wellsworth, causing Edward and BoCo to be trapped, but Belle is nervous about fighting a big fire without Flynn.
- James and Flynn - James thinks Flynn's job is easy, but is proven wrong when a fire rages at Ulfstead Castle.
- Oliver's Sea Rescue - Oliver sees a baby whale being hunted by some whalers so his driver calls Captain to stop the whalers.
- Duncan and Mike - Duncan and Mike form a rivalry.
- George and Buster - George meets Buster and the two become good friends.
- Donald and Douglas
- Bill and Ben
- The Diesel
- The Works Diesel
- Pip and Emma
- 'Arry and Bert
- Diesel 10
- Sir Handel
- Peter Sam
- Mighty Mac
- Annie and Clarabel
- Old Slow Coach
- Slip Coaches
- Jerome and Judy
- Max and Monty
- The Fat Controller
- Miss Jenny
- Sir Robert Norramby
- Farmer Trotter
- Trevor (does not speak)
- Jem Cole (does not speak)
- The Vicar of Wellsworth (does not speak)
- Sodor Brass Band (do not speak)
- Sam (cameo)
- Spamcan (cameo)
- Old Stuck-Up (cameo)
- Stafford (cameo)
- Taro (cameo)
- Culdee (cameo)
- Hector (cameo)
- Tiger Moth (cameo)
- Owen (cameo)
- Merrick (cameo)
- Stephen Hatt (cameo)
- Bridget Hatt (cameo)
- The Thin Clergyman (cameo)
- The Storyteller (cameo)
- Cyril the Fogman (cameo)
- Nancy (cameo)
- The Fisherman (cameo)
- Stepney (stock footage cameo)
- Logan (mentioned)
- Mr. Percival (mentioned)