Rusty is an orange Diesel Engine who works for the Skarloey Railway. He is Mr. Percival's only diesel.
Rusty primarily shunts trucks at the incline and the transfer yards. One day, Rusty was having a rest when he saw a flaming truck shoot through the tunnel, colliding with and setting ablaze the Skarloey Railway's coal supply. When Flynn arrived and was out of water, Rusty saw Peter Sam approaching and suggested using his water to put out the fire. Rusty's ingenuity helped alleviate the situation.