D199 is a rude diesel engine from The Other Railway.
D199 was built in the 1963 at Derby Works. In 1967, he came on trial to Sodor with another diesel engine, Bear. D199 soon made himself an enemy of the steam engines when he claimed that "steam engines spoil our image". Vulgar noises greeted this, until Duck and Bear managed to shut up D199.
The next day, D199 ironically failed with a train of oil tankers at a signal box, blocking the crossing. Henry, whose regulator had already jammed, came to help. However, after Bear's ejector leaked, making him unable to pull his passenger train, Henry was asked to help him as well. Henry, with some help from Bear, was still able to move and bravely pulled D199, the oil tankers and the passengers to the next station. Sir Topham Hatt was not impressed, and D199 was soon sent home in disgrace. However, his companion Bear was given a second chance.