Mini conspiracy to do with lrt actually because this has been rotting my brain. The timeline doesn't necessarily make sense because there is like a small ocean of time between the unplugging of TurboTime and Turbo's incursion into Sugar Rush, BUT HEAR ME OUT!
So we know that the visual design, vocal flair and body language of King Candy is HEAVILY inspired by Disney's Mad Hatter from their original animated Alice in Wonderland (1951). The resemblance is extremely deliberate. The hair, the high collar, the iconic lisp, the presentation.
But if we look at King Candy's visual design when compared to the other human avatars of SUGAR RUSH, our little faux monarch here does NOT STYLISTICALLY MATCH UP!
The racers of Sugar Rush are very clearly emulating a typical cutesy Japanese 'chibi' style. Round heads, big eyes, little noses, and legs that (while not so long as to be anatomically realistic) fit the proportions of their bodies. Their outfits are sleek and their silhouettes are quite thin.
King Candy does not follow this same design philosophy at all (and it's for this reason that I also personally believe that King Candy's appearance as a whole was a fabrication of Turbo's, rather than an unfinished NPC character whose model he commandeered).
I think an interesting in-universe explanation for King Candy's appearance could come from another game. One which Turbo would have known well.
After all, TurboTime had had a neighbor in Fix-It Felix Jr.
While their design language definitely does not line up 1:1, I see more of Felix in King Candy's appearance than I do the likeness of any Sugar Rush avatar. There are some commonalities in the facial proportions of King Candy and Fix-It Felix. Their heads are taller, eyes are smaller, and their mouths are wider. And then there is the nose, which is to me and my delulu brain the most obvious visual similarity between these two.
So. Say you're a societal pariah after doing something seriously taboo, and you need to blend in with a group of newly-arrived strangers in order to avoid being caught and punished for your misdeeds. There's not much time, and you need to get your affairs in order before anyone realizes what you're doing.
I think that, with his take-over of Sugar Rush being an extremely time-sensitive ordeal, Turbo had very little chance to devise the perfect disguise. So he cheated just a bit, took inspiration from a place that was familiar to him.
His own appearance, ghoulish and grey, dressed in blazing red over stark white, that would never fly in such a whimsical world. But he once knew a cast of characters with designs that all the Players found appealing at that time, and he fell back on that knowledge to craft his royal façade. All he knew for sure was that his avatar had to be cute, colorful and coherent.
The end result definitely doesn't scream Sugar Rush when you really scrutinize it, but it held up for fifteen years. Fifteen wonderful years full of racing and ruling and winning to his heart's content. Turbo was satisfied, maybe even truly happy.
I wonder if part of his apparent surprise during the Big Twist Villain Reveal(tm) came from him not immediately recognizing the ashy grey skin beneath the mask he'd built more than a decade ago. After all, he'd spent right around half of his entire life as the one and only King Candy, the benevolent monarch and best racer of Sugar Rush.
He would have been more than happy to leave his loathsome original avatar behind with the rest of the eight-bit era. It had done him no favors even when he wasn't old news just yet.
How unfortunate for him that the pesky Glitch had different ideas.