Male ADHD!Twilight, Female Jerk!Spike, Everyone else is canonically the same personality-wise but I can't say the same for gender.
Warning: Sexual References, Off-Character Rule 63 on some characters, swearing, rather harsh backstory, constant reminders of how Dusk Shine is best pony, everypony hates main character, and more.

Dusk Shine is a genius with a horrible case of Attention Deficit Hyperactivity Disorder, he cannot sit still for more than five minutes without becoming jittery and unfocused, unable to focus on one thing at a time, and uncontrollable impulsiveness. Despite this disorder, Dusk Shine has gone on to do many great feats and accomplishments.

Dusk Shine shows pride in his talent and accomplishments, maybe a little too much. Actually excessive to the point where many psychologists believe Dusk Shine has a God-like Complex. Actually, Dusk Shine just thinks he's better than everyone.

If only Dusk Shine wasn't such an annoying, selfish jerk to Celestia by mistake, he wouldn't be forced to watch over the preparations of the boring Summer Sun Celebration instead of preparing for the return of Nightmare Moon.

Dusk Shine's Superiority Complex is brought to you by inspiration from this chap.