The article is about characters from Thomas & Friends, that have appeared in the films first.
Thomas and the Magic Railroad was the first theatrical Thomas & Friends movie.
Diesel 10 (voiced by Neil Crone in the film/voiced by Matt Wilkinson in the UK and the US; Misty Island Rescue onwards) is a large cunning darkly comedic diesel engine with a claw (which he calls "Pinchy") extending from his roof. He was the main antagonist in Thomas and the Magic Railroad. Thomas said that he is rated "10 out of 10 for devious deeds and brutal strength". When he first came to Sodor, he hated steam engines so much that he made a goal to get rid of them once and for all. He tried to destroy "Lady", the magic engine that brings a magic railway and the steam engines alive. Although this plan failed, he was able to crash Lady causing her to be severely damaged. Her caretaker, a man called Burnett Stone, brought her back to his workshop in Muffle Mountain where he spent many years trying to bring her back to life. Diesel 10 repeatedly terrorized the steam engines and "Twinkle Toes" (his nickname for Mr. Conductor) in an attempt to track down Lady and the Magic Railroad.
Diesel 10 recruited two other diesel engines, Splatter and Dodge (who he collectively referred them as "Splodge"), to help him find Lady. However, the diesels grew tired of Diesel 10's attitude at the end of the film, and refused to help or follow him when Lady and Thomas returned to Sodor from Magic Railroad. Diesel 10 chased Lady and Thomas until the three came to the collapsing viaduct. Lady and Thomas were light enough to make it across, but unable to stop, the track couldn't hold Diesel 10's weight and it collapsed from underneath him, causing him to fall off the broken viaduct and land in a barge filled with sludge below and then he got in trouble with Sir Topham Hatt, The Fat Controller.
Diesel 10 is olive-coloured.
Diesel 10 reappeared in Calling All Engines!. Diesel 10 is feared by the engines and first appears when Thomas and Percy are at the scrapyards. When they see Diesel 10, they get scared and decide to return when he's gone. Thomas tries to go to other places but leaves when he finds Diesel 10 there. In the end, Thomas goes to Diesel 10 for help to move some derailed trucks and he agrees.