Silver, Sonic and Shadow

Mission first. Silver has come from the future to right the wrongs of the past. His primary goal is to protect the world, and he's willing to go to great lengths to achieve that goal.
Seriousness without cruelty. He's not mean or cold, just very responsible. He often appears tense because he bears a huge responsibility.
Naivety and sincerity. Silver can be awkwardly straightforward: he trusts people, takes everything literally, and sometimes doesn't understand sarcasm. Because of this, Sonic teases him, and Silver genuinely doesn't get the joke.
Optimism against all odds. Even when the situation seems hopeless, he doesn't give up. His "I'll find a way" isn't bravado, but a realistic approach to life.
Willingness to sacrifice. Silver isn't afraid to risk himself for others. This isn't posturing, but a genuine sense of duty.
Psychokinesis as a reflection of character. His abilities are about control and defense: he moves objects, creates barriers, and stops enemies. In combat, he uses not only speed but also intelligence, calculating his options.

Fur. Silvery-white, almost metallic. It looks like it's from another time—and that's intentional.
Needles. Five needles of varying lengths, tilted backwards, as if caught in the wind. The two longest reach almost to the shoulder blades. The shape of the needles gives it a streamlined silhouette.
Eyes. Golden irises with distinct black lines around the edges—this adds seriousness to the look and makes it easily distinguishable from other hedgehogs.
Face and skin. The muzzle and inner ears are peachy, and the nose is black. Overall, the features are soft, but the expression is almost always collected.
Clothing. White gloves with circular aquamarine symbols. Gold cuffs with stripes. Dark blue boots with a white stripe, aqua toes, and gray soles and heels. The boots have gold cuffs with red stones: this is not just decoration, but part of the "futuristic" style.
Accents. In some scenes, a faint glow is visible around him—a hint of psychokinesis.

24/7 energy. Sonic is pure impulse. He doesn't like to stand still, either literally or figuratively. If there's a road, he'll run it. If there's a problem, he'll solve it while you're still trying to figure out how to start.
Lighthearted and humorous. He loves to tease enemies and friends, cracking jokes right in the middle of battle. His "I'm outta here!" and signature smirks are part of his persona. Justice without pathos. He saves the world not because he has to, but because, "Well, who else if not me?" And he does it with a smile, without heavy monologues.
Freedom-loving. Dislikes restrictions, plans, and "sitting in a corner." He needs space and speed to feel alive.
Loyalty to friends. He may seem frivolous, but when it comes to his loved ones (Tails, Knuckles, etc.), he becomes extremely reliable.
Excitement and challenge. He loves racing, competition, and situations that test his limits. For him, a battle is also a race, where he has to be faster and smarter.

Color and fur. A bright blue, a rich shade that immediately catches the eye. The fur is smooth, but its shape gives it a dynamic appearance—as if it's always in motion.
Quills. Seven long quills protrude from his head: four point upward, three downward. This is his signature feature, making his silhouette recognizable even in tiny pixel art. His face is peach-beige, his nose is black, and his eyes are large, with emerald-green irises (the shade varies slightly between games). His gaze always seems to be "on the move": lively and eager.
Clothing. White gloves and red boots with white cuffs and buckles. The boots have a distinctive shape: they look as if they were made for speed. Some games and artwork add details like straps, but the basics are always the same. Details. A small ponytail, a pair of extra spines on the back. Overall, the proportions are such that the character appears light and springy—as if ready to take off at any second.

Shadow isn't just a "dark Sonic," he's a character with a very difficult background and a truly contradictory personality.
Cold, but not heartless. He almost always maintains a detached demeanor, speaks briefly and to the point, and doesn't overextend himself. But that doesn't mean he doesn't care: he simply doesn't like to show his feelings. In critical moments, he can make difficult choices that others can't handle. Obsessed with duty and memory, his main driving force is his promise to Maria. The phrase "I'll keep my promise to Maria" is literally his internal compass. Because of this, he often puts duty above personal comfort and even safety.
Proud and independent, he hates being bossed around and won't blindly obey. If he helps, it's because he decided to, not because he was asked. This explains his constant clashes with other heroes: he doesn't acknowledge authority figures unless they're close to him.
Restrained rage. When someone threatens those important to him, or when the memory of Maria is hurt, Shadow can flare up. His anger isn't chaotic, but very focused. It's not hysterical, but rather "I'm going to destroy everything because that's what needs to be done."
Hidden care. He rarely says, "I'm worried about you," but he does. He can save someone, then mutter, "Don't get in my way," and walk away. For fans, it's a classic: "rough on the outside, but a good guy deep down."
Internal conflict. He constantly struggles with what he was created to be: a weapon, a tool. Hence his doubts: "Why do I exist? Am I a person or just a project?" This conflict is revealed differently in different games, but it is always there.

Straightforward and sarcastic. He loves short, snappy phrases. Sometimes he incorporates dark humor or irony—but just enough to avoid seeming friendly.

Fur. The primary color is black. However, there's a noticeable patch of white fur on the chest. The quills on the head. There are six of them. Four curve upward, and two (in the middle) curve downward. There are red stripes on the quills themselves, as well as along the edges of the eyes, arms, and legs. Incidentally, artist Kazuyuki Hoshino was inspired by traditional kabuki makeup for these red accents. There's also a theory that the color scheme is connected to Black Doom, the alien race whose biological samples were used to create Shadow.
Face. The muzzle is tan (brownish), as are the insides of the ears. The nose is medium-sized and black. The eyes are pointed with red irises. There are also red lines at the corners of the eyes.
Other details: Shadow has a pair of quills protruding from his shoulder blades and a small, pointed tail.
Clothing and accessories. He wears white gloves with black cuffs and red "tabs." He has "Limiter Rings" on his wrists and ankles, which help control the amount of energy he expends. Another signature feature is his special "Air Shoes," which are a combination of white, black, and red. The soles have nozzles that blow air, allowing Shadow to hover and accelerate to supersonic speeds. The cuffs and details on his boots echo those on his gloves.