Day of the Diesels (Rainbow Rocks style) is a new movie.
Diesel 10 and the Diesels try to get everyone to admire them by turning Percy against Thomas. Now it's up to Thomas and the others to free Percy and the humans before the Diesels take their popularity too far.
The film kicks off with Diesel 10 and the Diesels feeding off the negative energy of other engines. Diesel 10 then sees the steamies using the magic of friendship to defeat Spencer and his goons. The Diesels and their fearless leader plot to use it to become more popular.
A few days later, Spencer has been redeemed and wants to show everyone that he has changed. No one trusts him though, except the steamies. When Sir Topham Hatt mentions the events of "Hero of the Rails" during his speech, everyone glares at Spencer and Spencer hides his face. Nighlock glares back at them, not happy they don't forgive as easily. Magneto says they are as cruel as all humans, and storms out. Later, Spencer laments how he'll never live his past mistakes down. The steamiest and Code Red comfort him about it. Quicksilver even reminds him that every Code Red member, except Shark Fleet, Blue Eagle, Justice, General Maximoff, and Malfunction, committed crimes before they became members. The steamies decide to cheer up their friend by singing "Better Than Ever". As they do, they gain robot bodies, impressing Nighlock and Apocalypse. The robot bodies disappear when the steamies stop singing. James can't believe that happens whenever they play. Magneto walks in and apologizes for his outburst earlier. Gordon, however, cares little, letting his band leader egotism show after James and Toby both express disbelief at the strange phenomenon. Nighlock face palms, while James just says "Your band?!" and then Gordon replies that it was his idea to start this band but Deadpool interrupts on the PA system. He tells Spencer to report to the main foyer. He then yells at Snips & Snails, telling them not leave their garbage on the floor.