Gemini

Gemini or Gemi and Mini are Celestial Spirits and one of the 12 Golden Zodiac Keys. They possess the ability to mimic the appearances and abilities of others.

Appearance
Gemini are two individual twins of a single Celestial Spirit. They are both small alien-like creatures with two strands of hair. They both wear shorts. Gemi has a smile like "V" shape while Mini has an upside down "V" for a mouth. Gemi has a sash running from his right shoulder to the left side of its waist, the opposite being true for its twin.

Oración Seis arc
Gemini first appears after the guild alliance leaves the Blue Pegasus' base. While posing as Ichiya, they reveal themselves after stabbing Jura in private before leaving with Angel. They are later summoned by Angel during the Oración Seis's skirmish with the Light Team and attack Lucy Heartfilia and Gray Fullbuster in the confusion. They later pose as Gray, and incapacitate Natsu by tricking him onto a raft, bringing about his vehicular motion sickness. As Gemini is about to deal the finishing blow, Lucy interferes by summoning Sagittarius. Gemini attempts to attack Lucy, but their attack is blocked by Hibiki. After retrieving information on Hibiki from Gray's memories, they assume Lucy's form and use Hibiki's weakness of women by exposing Lucy's breasts, much to the real Lucy's dismay. Gemini, with Lucy's abilities, commands Sagittarius to attack Hibiki. Lucy forces Sagittarius's gate to close, only for Gemini to re-summon Sagittarius. When Lucy tries to force him back again, she is unable to since Gemini called him and only they can force close the gate. Angel appears and challenges Lucy to a duel. Gemini, wielding Caelum, seduces and defeats Taurus and attacks Lucy after she exhausts her magic. As she is about to strike the finishing blow, Gemini recalls Lucy's memories and cannot bring themselves to attack her after seeing Lucy's love for her Celestial Spirits. In her frustration, Angel banishes them back to the Spirit World.

Later, in Nirvana, having arrived at the third Lacrima, Lucy reveals to Happy that she has no magic power left, but that she will not give up fighting until the very end. However, Gemini summons themselves in order to help her destroy the Lacrima. Taking Lucy's form again, they summon Taurus and have him smash the Lacrima simultaneously with Natsu, Gray, Ichiya, Wendy, and Erza. After wards, Angel is arrested, breaking her contracts with her spirits. Gemini, along with Scorpio and Aries, seek out Lucy and form contracts with her instead.

Edolas Arc
Gemini plays a large part in Lucy's plan to get information from King Faust. Since interrogating him wouldn't work, she hoped that Gemini would be able to transform into him and steal his thoughts, but the group gets captured before the plan is put into action.

Magic and Abilities
Mimicry: The Gemini twins has the ability to transform into anyone that they have contacted. With this, Gemini is well suited for purposes like infiltration and information gathering/retrieval


 * Transformation: The Gemini has the ability to transform into anyone flawlessly. 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). Though it is most unlikely that they could also mimic the subject's level of magical power to the same caliber. Gemini, however, can only hold the transformation for five minutes, and they must touch the person in order to transform. This may be due to the summoner's magic capability rather than their own. 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. Gemini can only retain the capability to transform up to two people, and any more additional transformation requires them to erase one of the transformed forms. It must be noted that it is not known if in their transformations they can wield the same power as the person they are copying.


 * Transformation into Ichiya: As a Ichiya they can use Perfume magic. They also said that he's thinking only about dirty staff.
 * Transformation into Lucy: As a Lucy Gemini can use a whip and even summons other Spirits.
 * Transformation into Gray: As a Gray they can use Ice Make magic.

Trivia

 * Prior to their proper introduction in Chapter 133, they have already appeared on the cover of the chapter release twice, Chapter 98 and Chapter 122.
 * Interestingly, Gemini is the only Celestial Spirit shown to be able to summon other spirits.
 * In Chapter 165, when Lucy makes her contracts, Gemi and Mini have their sashes running from the same shoulder to their hips, but it is corrected in the next panel below.