Gemini are two individual twins of a single Celestial Spirit. They are both small creatures with blue colored bodies and two antennae. They have small, black, beady eyes with white pupils. They both wear shorts, Mini wears orange shorts, and Gemi wears black ones. Gemi has a "^" shape for a mouth, while Mini has an "v" for a mouth. Gemi has a sash running from his left shoulder to the right side of his waist and Mini has a sash running from her right shoulder to the left side of her waist.
During the fight of Lucy against Flare Corona, Gemini appeared with a different outfit. They are now both wearing white belts.
Depending on the Mage they're contracted with, they undergo personality changes to reflect said Mage's personality. While under Angel, they were sadistic, cruel, and clearly enjoyed tormenting other people like she did. However, they had a change of heart when they heard Lucy's thoughts of compassion towards her spirits, as well as her principle of treating her spirits as equals. When Lucy was unable to use her Magic during the battle with Angel, they came to her and were willing to help, even though they betrayed their master.
Gemi and Mini are generally shown to be very joyful Spirits. While waiting for orders, they dance and make various poses. They don't seem to be very shy, as they have no problems with showing their breasts to their enemies (they had transformed into Lucy at the time, and were under a contract with Angel).
Copy Magic: The Gemini twins have the ability to transform flawlessly into anyone that they have contact with. With this, Gemini is well suited for purposes like infiltration and information gathering/retrieval. Once transformed, they will gain the transformed person's knowledge, Magic and their recent thoughts (if not while they are thinking about them in real time). When they recall memories, they talk in a bullet style listing; the amount of information that they can access is, of course, limited to the knowledge that the genuine counterpart is actually aware of, and nothing more beyond that. However, Gemini can only hold the transformation for five minutes, and they must touch the person in order to transform. Gemini can only retain the capability to transform up to two people, and any more additional transformation requires them to erase the older one of the transformed forms. Also, Gemini's transformation is restrained depending on its owner. It can only transform into people with the same level or lower Magic Power as their owner. Anyone with a higher Magic Power than their owner will result in an incomplete transformation. Gemini can also transform themselves into a near target without touching, but this restrains the appearance of the clone to the appearance that it had last time they have contact.
- Mimicking Lucy: As Lucy, Gemini uses a whip as a weapon. They can even summon other Spirits, and control Spirits summoned by the original Lucy. Gemini can also distract male enemies with her attractive body. During the Grand Magic Games, Lucy combines her Magic Power with Gemini transformed into her and together they cast Urano Metria. However, the spell was cancelled by another Mage before its effects could be seen.
Levitation: Gemi and Mini can both walk on the ground and float in the air. This ability also allows Gemini to make strong and fast aerial attacks with an aura of Magic Power around them.
Immortality: As Celestial Spirits, Gemi and Mini cannot die, unless they are somehow forced to stay in the Human World