He first appeared in the fan-fiction when Marco encountered him in Father Time's throne. He smiled super sinisterly and stared into Marco's soul menacingly. As he came closer, Marco got more scared. He then says what he has seen and heard about him. But as the confrontation went on, he explained everything that happened all these years: The Great Monster Massacre and whatnot. He even explains the bad things he did to Star's wand. As Marco gets angry at Diesel, the time lord glares at him but laughs off. As he warns him to not underestimate or over cross the rules of space and time, he went back to the throne. He was obviously hiding something sinister. Something that was kept supreme top secret since the day Star first came to Earth.
He appeared when Jackie found a strange device that looked like a time stopping device on her locker. She then was scared and when Diesel smiled like a rogue “perv”, she ran for her life. But before she could escape him, he used his time stopping laser gun at her so she could freeze her like freezing time itself. He laughed as he teleported back to the “Freeze” dimension.
When Jackie was moving again, he warned everyone in the school about him. Meanwhile, Diesel repaired his time-stopping suit and gadgets. He ran faster than Marco and Star, who were chasing him. And as they arrived to earth, they noticed he was terrorizing the whole town. They had to stop him, but as Star took her wand, Diesel quickly destroyed it and went to Ludo's dimension. Star and Marco had to get there.
Later, at Ludo's destroyed castle, Toffee was with Diesel, until the time lord himself betrayed the lizard by caging him in the same cage of super glass/plastic Marco was trapped in. Ludo was with Star and Marco, because he was ready to help. So, all of Star's former enemies united against Diesel. As the clash started, everyone passed out. Except Star.
Before Star could defeat him, she fell down unconscious as Diesel took out his time stopping bomb and put it down. But before he could win, he was immediately stopped by Toffee who was reformed. Beelzebub exploded, but everyone has learned that he has survived and that the evil time lord plans to have his revenge as he flies off to his home dimension he calls Fasad.
- Ludo and Toffee are thought to be the main antagonists (despite calling it a Big Bad Ensemble), Diesel is revealed to be the real true main antagonist of the whole show because he was 500% more evil and had far bigger plans than anyone else.
- He is certainly the darkest Disney XD villain.