Plue

Plue a.k.a Nikora, "The Canis Minor", is a Silver Keys' Celestial Spirit that has no obvious combat abilities and is stated to usually be used as a pet for low-powered Mages, but is as powerful as any other character in the game Fairy Tail Gekitotsu! Kardia Daiseidou. Lucy Heartfilia seems to use hers, named Plue, as merely a comical character for his summoner. Nikora keys are shown to have been sold for as little as 20,000.

Appearance
Plue is a short, stout white creature (who is commonly referred to as a dog by Natsu Dragneel) with bland eyes and a golden horn-like nose (reminiscent of a carrot from the side, thus giving him the slight appearance of a snowman). His body is often shaking nervously, though this doesn't always occur. He cannot speak besides saying "puu-puun", although Natsu seems to be able to understand this. He mostly communicates by using gestures and motions which Lucy finds adorable.

Personality
When Lucy first contracted Plue, he only agreed to be summoned on Tuesdays until Thursdays (in the manga)/ Sundays (in the series English dub). As the series progressed, however, it was shown that Plue is available anytime and that Lucy doesn't seem to summon him and yet he appears. Because he is not designed for combat, he serves as a cute pet for Lucy instead. Plue enjoys sweets and shares a close friendship with Happy. Their good relationship could be accounted for the fact that they are always together during Team Natsu's missions, as well as their almost similar attitudes. Happy and Plue often tease Lucy and Loke.

Macao arc
In order to show Natsu and Happy how contracts with Celestial Spirits are made, Lucy summons Plue for the first time and demonstrates it to the two. However, because of Plue's peculiar appearance, Natsu and Happy saw him as a failure. When Plue speaks for the first time, it was shown that Natsu understands him, while Lucy does not.It was Plue who first suggested to Natsu that he and Lucy should become a team.

Galuna Island arc
In a battle against Sherry Blendy--a Mage capable of controlling anything that is not human, like puppets--Lucy purposely summons Plue, knowing he will be used against her. Once under Sherry's control, "evil" appears on Plue's forehead, his eyes glow, and he runs aggressively towards Lucy. His noncombatant nature, however, prevents him from harming Lucy despite the flurry of kicks and punches he releases at her lower half. Once Sherry releases the control on Plue, he immediately apologizes to his owner, and returns to the Celestial Spirit World.

Loke arc
After arguing with Loke, Lucy leaves with Happy and Plue, and the latter seems to recognize Loke. Plue is later summoned along with all of Lucy's Spirits in order to persuade the Celestial Spirit King to let Loke return to the Celestial Spirit World.

Daphne arc
Note: Events in this arc occur only in the anime and do not constitute canon material. Lizardmen attack Erza and Lucy. Realizing that the Lizardmen only mimics the skills and abilities of their opponents, Lucy summons Plue, changing the Lizardman she is fighting to a similar size. Plue then starts to dance, gradually gaining speed. The Lizardman starts to mimic his moves, but is unable to keep up with Plue, and soon vanishes, defeated.

Tenrou Island arc
Note: Events in this arc occur only in the anime and do not constitute canon material. After having three of her Celestial Spirits defeated, Lucy decides to summon Plue to fight Kain Hikaru. Immediately after being summoned, Plue starts to dance and his cuteness temporarily entrances Kain. However, Kain recovers and decides to eat him, causing Lucy to scoop him up and run.

X791 arc
Upon returning to the present time, Lucy heads home with Plue, but was not allowed in her apartment by the landlady because of the seven years of rent she owes. Lucy then talks to Plue about her father, whom she finally decided to visit.

Key of the Starry Sky arc
Note: Events in this arc occur only in the anime and do not constitute canon material.

Grand Magic Games arc
While training for the Grand Magic Games, Lucy and her friends were brought by Virgo to the Celestial Spirit World, where the Spirits, headed by their King, celebrate their return from Tenrou Island. During the festive, Plue greets Carla and Happy, together with other tens of Nikora's behind him, who lift the two into the air. Plue then dances with Happy as Lyra plays her harp.

Magic and Abilities
Immortality: As a Celestial Spirit, Plue cannot die, unless he is forced to stay in the Human World somehow.

Megane-Fairy
Lucy lends Shinagawa Plue's Gate Key so he may summon Plue in order to demonstrate his ability to perform Magic to Makarov. However, he ends up summoning a deformed version of him.

Welcome to Fairy Hills!
Plue accompanies Lucy in investigating a job request from Fairy Hills where they meet Hilda, the client, who assigns Lucy for the job.

Happy in Boots
Plue is the first "animal" that Happy captures with his sack and also the first present to the king and princess of the kingdom.

Fairy Academy - Yankee-kun and Yankee-chan!
Plue appears as the Fairy Academy principal during the assembly called by Carla as a lecture to the delinquent students. He delivers his speech in a dance that is only understood by Natsu and Carla.

Video Games
Plue appears as a playable character in DS Game Fairy Tail Gekitotsu! Kardia Daiseidou.

Fairy Tail Gekitotsu! Kardia Daiseidou
In the video-game Fairy Tail Gekitotsu! Kardia Daiseidou, is a playable character. In this game, possess the following moves:
 * Main: Plue Attack
 * Sub 1: Plue Copter
 * Sub 2: Plue Healing
 * Sub 3: Plue Eye
 * Super: Plue Sonic

Major Battles

 * Lucy Heartfilia (owner) vs. Sherry Blendi
 * Erza Scarlet & Lucy Heartfilia (owner) vs. Daphne's Lizardmen
 * Lucy Heartfilia (owner) vs. Kain Hikaru (Anime Only)

Trivia

 * Lucy's quote when summoning him is: "Open a Gate of the Canis Minor! Nikora!".
 * Apparently, it was his idea for Natsu to make a team.
 * Nikora is the only "dog" Happy likes.
 * Happy plays a trick on Lucy by feigning a voice for Plue. Happy makes a reference to Rave Master, saying that Plue is the servant of a hero with a sacred stone, Haru and the Rave respectively.
 * Mirajane believes that Plue is the strongest among all of the Celestial Spirits.
 * A special restriction made by Hiro Mashima stated that the number of lines on Plue's nose must be 5, no more, no less.
 * Plue gets very wrinkly in hot water.
 * Plue's character was featured in Hiro Mashima's previous work, Rave Master.
 * For Rave Master, Plue, who is created Hiro Mashima, is originally a doodle (unknown volume). It is interesting to note though, that it can be assumed Plue has been a Rave Master Guardian for all his creation time, even though it was never stated. Another note for the pronunciation of Plue's name, (in Hiro Mashima's notes - Rave Master volume 3) Plue is pronounced like the color, "Blue."
 * In the first episode of "Fairy Tail" (english dub) Lucy called Plue's key "Canis minor the blue dog" instead of "Nikora the Canis minor".
 * In the Manga chapter 1 Lucy called Plue's key "White Doggy" instead of "Nikora the Canis minor".
 * In the Manga there were two other keys beside Plue's key in a case.
 * In chapter 262, Lucy, Natsu, Gray & company are invited into the Spirit realm by Virgo, and a welcoming back party is put on for them. Happy and Carla are greeted by Plue, who is followed by a mass of other Nikoras. This is the first time that other spirits of the same silver key are seen.