Thomas & Friends in 4-D: Bubbling Boilers, also known as Thomas & Friends: Bubbling Boilers, is a 4-D attraction special episode with cinematography by SimEx-Iwerks Entertainment and animation by Arc Productions.
It is a big day on the Island of Sodor: Mr. Bubbles is throwing a bubble party. When Thomas arrives at the docks, he sees Cranky crossly unloading materials and crates for the party. Unfortunately, he cannot participate because he has to stay in one place. Salty is not worried, however, but he soon becomes concerned when Stuart, Cranky's friend distracts Cranky and he drops bubble liquid onto Thomas. Thomas is too much in a rush to go to the washdown. As he puffs, Thomas finds it hard to brake, as the liquid is making him slip. He finds it funny when bubbles begin to puff out of his funnel, but the fun is soon over when his signal turns red. After nearly hitting Emily, he puffs onto a separate track and crashes into the now boarded up Ulfstead Mine.
Thomas soon hits some mine trolleys and bumps into some rocks on the line. This causes the coupling to come loose, sending Thomas down one way, and sending his cargo down another. Thomas soon follows in pursuit of his cargo. Up ahead is a waterfall and Thomas notices two of the mine trolleys he knocked into are coming onto the same line. Thomas quickly puffs ahead and misses being hit by the two trolleys. Splashing into a waterfall, he lands unbalanced and is knocked off the rails. He feels terrible and to make matters worse, he does not know where he is. Suddenly, he sees Stuart, but Stuart flies away. Thomas begins to lose hope until Harold arrives with Sir Topham Hatt and Mr. Bubbles. Edward and Rocky soon arrive to lift Thomas back onto the rails.
Thomas tells them about his adventure, which gives Mr. Bubbles an idea. Soon, the party is relocated to the docks, but Cranky is not notified of this change. As the party begins, Sir Topham Hatt says that the party is dedicated especially to Cranky and as soon as Stephen puffs in with Mr. Bubbles and his bubble machine, the party begins. Cranky feels happy and claims that this is the best party ever. Stuart also claims that he is welcome as the party continues.
- Sir Topham Hatt
- Mr. Bubbles
- Some Workmen
- Edward (does not speak)
- Rocky (does not speak)
- Harold (does not speak)
- Gordon (cameo)
- Percy (cameo)
- Stephen (cameo)
- Diesel (cameo)
- Annie and Clarabel (cameo)
- Big Mickey (cameo)
- Sodor Brass Band (cameo)
- The Dock Manager (cameo)
- The Teacher (cameo)
- The Bird Watcher (cameo)
- The Blond-haired Boy (cameo)
- One of Dowager Hatt's Friends (cameo)
- The Welsh Bird Watcher (cameo)
- The Windmill
- Vicarstown Bridge
- Brendam Docks
- Sodor Shipping Company
- Ulfstead Mine
- Ulfstead Branch Line
- The Washdown (mentioned)
- John Hasler as Thomas
- Keith Wickham as James, Salty, Sir Topham Hatt, Mr. Bubbles, some people and some workmen
- Jules de Jongh as Emily
- Steven Kynman as Porter
- Matt Wilkinson as Cranky
- Joseph May as Thomas
- Rob Rackstraw as James
- Jules de Jongh as Emily
- David Menkin as Porter
- Keith Wickham as Salty, Sir Topham Hatt, Mr. Bubbles, some people and some workmen
- Glenn Wrage as Cranky
- While not a TV episode, this one takes place during the twentieth season.
- The Sodor Brass Band plays the Hero of the Rails opening version of Engine Roll Call as a fanfare at Brendam Docks.
- A remix of the original Thomas & Friends theme first composed by Mike O'Donnell and Junior Campbell from Seasons 1-7 is heard.
- An instrumental of the song I Do Like to Be Beside the Seaside can be heard during the end of the feature.
- It premiered at the Museum of Science in Boston, Massachusetts, USA on 9 April 2016 and will be playing there until April 2018.
- It premiered at the Columbus Zoo and Aquarium in Powell, Ohio, USA on 9 April 2017.
- This marks the first of a few things for Mr. Bubbles:
- The scenes of Thomas travelling through Ulfstead Mine and out through a waterfall are similar to the journey he took through Morgan's Mine in The Great Discovery.
- It is likely that Mr. Bubbles' bubble party was originally going to be at Ulfstead Castle since Thomas took the track to Ulfstead Mine which is located at the bottom grounds of the castle. Stephen's appearance at the party is further proof.
- Chris Renshaw takes over the role of composer starting from this feature onwards since Robert Hartshorne and Peter Hartshorne's contract ended after Sodor's Legend of the Lost Treasure.
- In the accident scene, it is shown that Thomas' body is not attached to his frames, as this goes visible for a little moment as they clip through the footplate.