Thomas & Friends in 4-D: Bubbling Boilers, also known as Thomas & Friends: Bubbling Boilers, is a 4-D 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.