For the Fusion counterpart, see Spinel (Fusion)
Spinel has a pink complexion, magenta eyes, a small pointy nose, and magenta hair that is styled into a pair of spiky pigtails. She also has three black lines underneath both of her eyes, reminiscent of running mascara. Her clothing consists of a dark magenta top, puffy pointed hot pink sleeves, puffy magenta shorts, hot pink wrist-length gloves, white stockings and a pair of magenta knee-high pointy boots. Her gemstone is located in the center of her chest, cut in the shape of an upside-down heart.
When reset to her original self, Spinel's overall design is more rounded in contrast to her current pointy design. She had black cartoonish eyes and her hair was styled into a pair of heart-shaped buns. Her top was white with more rounded pink sleeves and her boots become a pair of big magenta shoes. Spinel's previous color palette is also brighter than her current one which uses darker tones. Overall, her appearance was similar to that of a 1920s rubber-hose cartoon character. Her gemstone used to be right side up, resembling a normal heart.
For a brief time, she had a specialized, metallic attachment appearing to have been forcefully pulled out of place. It was soon removed thanks to Tempest Shadow.
Spinel is a playful, bombastic, yet dynamic sort of Gem who has a deep child-like demeanor around others and always tries her best to be enjoyable and fun to have around in a similar manor such as Pinkie Pie, but more mellow due to her past experiences. Being made to be a playmate to her owner, Spinel has a almost instinctual fondness for fun activities, namely games and such. This however does make her a bit clingy, and easily-trusting to those around her. Throughout the season she has shown to be very loyal to her friends, showing a deep attachment to them. This is best shown with Steven, who she calls her "Big Brother", and towards Garnet, who she sees as a mother figure.
Despite this, Spinel is also surprisingly intelligent, cunning, syndical and easily violent towards those she considers her enemies, even retaliating against The Diamond Authority simply over a grudge against them, and willing to kill all of Earth strictly out of spite. This trait shifts to her reset form immediately when she thinks Flint and Lapis are together, willing to poof Lapis Lazuli the first chance she got. This kind of behavior makes her highly unpredictable, enough for even Grogar to become wary around her during this state.
Spinel was created for Pink Diamond as her personal playmate before Pink got her colony on Earth, playing with her for hours every day within Pink Diamond's Garden. One day, she was told to wait in the Garden for Pink to come back, but she never did. She considered leaving to find her, but White Diamond found her and took her in, tricking her by saying she wanted to play with her. What resulted instead was Spinel being experimented on for the next few thousand years, leaving her emotionally and physically scarred with a metallic device attached to her head that causes personality shifts if activated.
When the White Diamond Space Station became abandoned and without power, Spinel eventually found her way to the piloting station, and took control of the spaceship.
The White Diamond Space Station crash-landed on Earth, Spinel coming out after all the Corrupted Gems inside escaped from it, her being found by the Harmony Gems. Spinel explains how she got in there briefly, and when she thinks they might take her back to Homeworld, she quickly begs to stay and become apart of the Crystal Gems, learning about their freedom from complaints by White Diamond's Hybrid Gems. She was eventually taken in, but they quickly find out about her dangerous personality, her desire to shatter the Diamonds for what they put her through specifically. However, after a brief encounter with Tempest Shadow (and being "freed" of her device thanks to her) she mistook the Harmony Gems' later talk about her as them turning her in to the Diamonds. Feeling betrayed, she quickly joins Grogar's Army for a time, and agrees to try and get rid of them. Later she arrives back on Earth with both a giant Gem Injector, along with a Rejuvenator to confront them - both which she got from White Diamond's Space Station. She manages to reset several Crystal Gems, along with Pink Diamond, and quickly calls for the giant Injector to start sucking life out of Earth. This however makes Grogar turn on her, wanting to take over the world and not destroy it, her fighting him out of sheer anger. During the whole ordeal, she starts to shift on who to trust once she meets Sunstonnie, admitting her mind's stuck in a weird place, just before she got hit with her own Rejuvenator.
Upon reforming and being reset, Spinel immediately grows attached towards Flint, considering him as her "new best friend" on the spot. For much of the time from there, she spent playing with Flint and basically being around him, despite his numerous attempts to have her stay away from him even for a short time. This all came to a head when Lapis Lazuli reformed, and tried hitting on Flint much to Spinel's frenzy. She tried to use a huge cutter on Lapis Lazuli, but she loses control over it and destroys a fair amount of Little Homeworld instead, finally making Flint snap and tell her to leave and that he's not her friend anymore. This starts making her remember her turmoil from her past, which Steven helps her remember by bringing her to Pink Diamond's Garden again. She returns to normal and regains all her memories while there, and she agrees to return to Earth and try again.
Ever since this decision she has stayed with Steven Universe, thinking of him as her older brother and helps him however she can.
During the three-part finale, Spinel stays with the rest of the Harmony Gems as the Crystal Gems and Elements of Harmony left the Realm of Corners, Spinel promising that she wouldn't lose herself and be a strong and brave Gem for him. She stuck with Starlight Glimmer inside of the Tindalos den, fighting off anyone who tried to break into it as a last line of defense throughout the battle. When she learned that Grogar figured out their plan, Spinel left the group with Lion and Blue to try and find where Steven is to see if he was alright. She eventually finds him and the remaining Gems in the Supreme Kindergarten, and as much as she tried not to, broke down and pleads for Steven to come back, not wanting to be alone anymore. She remains with him until he revived himself, and she willingly helps him revive the rest of the Gems and Ponies for a second attack on Grogar. She remains with Steven and Connie throughout the final battle against Grogar and Sumu, promised that they will not leave her alone again. She and Connie help Steven during the final battle inside Sumu's core.