Imagine when the little guy is sick. He's got a cold, not big deal for a regular cat but for Misto everything is intensified. He hates being cold so having a fever literally bed binds him.
His powers go haywire and we get things like random portals opening and poor Jellicles falling into them especially if they're napping, they're always safely returned to the junkyard don't worry.
Electricity explodes and lightning strikes whenever he sneezes.
He talks in his sleep and tends to speak latin but unfortunately this leads to him accidently causing plagues of bugs and small pests, the jellicles don't mind that bit because well free food, storms which they hate, but he also summons other demons by accident. Jemima takes care of them when this happens.
He also has a habit of teleporting around the junkyard in his sleep and Tugger cant keep up with him. Luckily Jemima can and she finds it hilarious where he ends up.
He needs to be warm because he is the alumnus of heaven and hell so Tugger gathers up as many blankets as he can not that Misto stays in them for long.
He HATES medicine with a passion and anyone who tries to give him some will feel his wrath. Its the only time he's truly aggressive.
His fur becomes extra electric because his powers are in overdrive. And his eyes will glow like little torches.