Rave Master

Rave Master (also called Groove Adventure Rave or simply Rave in Japan) is a previous manga of the author of Fairy Tail, Hiro Mashima, which ran in Weekly Shonen Magazine from 1999 to 2005. It tells the story of Haru Glory, a teenager who becomes the second Rave Master and is destined to bring peace to his world and save it from the threat of Dark Bring (Shadow Stones in the English version). Along the way, Haru gains friends who join him on his quest and they slowly unravel the mystery of the Rave Stones (his power source), the Dark Bring, and his destiny and how it affects those around him and the fate of the world in general. In April 2011, Hiro Mashima released a crossover of Fairy Tail and Rave Master entitled Fairy Tail x Rave Special.

Many elements of this series pop up in Fairy Tail often. Many characters have similar designs to Rave Master characters, most notably:

Rave Similarities

 * Plue, Haru's guide, is one of Lucy's Celestial Spirits
 * Jellal Fernandes has the same facial tattoo and hair color as Sieg Hart. Jellal's Thought Projection's alias, was Siegrain.
 * Etherion originated from Rave Master, and it is a highly destructive Magic in both series.
 * Oración Seis is also a legacy from Rave Master, in which it is similarly portrayed as an élite group consisting of six powerful individuals.
 * Haru's Rave stone in necklace form resembles the necklace worn by Gray Fullbuster. Though the latter does not transform.
 * Erza Knightwalker's spear has the same name as Haru's Ten Commandments sword, as well as the same forms.
 * Heart Kreuz was first seen in Rave Master and is a popular fashion brand among young females.
 * Musica Sword, Sword obtained by Lily in episode 119. Sword named after Musica, the blacksmith.

Rave Appearances
One can also spot characters from Rave Master in the background. The cover for chapter 91 even featured Lucy and Natsu dressed as Haru and Elie from the series. For more information of the series, check the Wikipedia article on Rave Master or its Wikia site.
 * Erza's armor has the same 'Heart Kreuz' logo as Elie's tank top.
 * Romeo Conbolt wears a shirt with Nakajima's face in his first appearance.
 * Erza Knightwalker's Saint Spear the Ten Commandments transforms into Silfarion, Mel Force, Explosion, Gravity Core, Blue Crimson, and Rune Save, all with identical abilities.
 * Let and Julia standing in the crowd of people in chapter 47 page 20
 * Casino in Chapter 75 has a Ruby's figurehead.
 * The brand 'Heart Kreuz' is featured prominently (All Requip Amour has logo featured in some way or other, Lucy's Clothes, and both Erza and Lucy have Heart Kreuz Bags, Suitcases, etc.)
 * In the Omake Lucy's Photo shoot, Elie, Julia, Belnika, Musica, Ruby and possibly Griff (because it is of the same species as Griff and it has a perverted look on it's face) make a small appearance.
 * Griff makes appearances often, the most prominent being in the anime where Happy is chewing him instead of fish.
 * Griff explains Mest's memory Magic in chapter 215 on page 10.
 * Gray wearing the same white bringer in the cover for chapter 225.
 * In chapter 102, Elie ,Julia, Griff, Musica (and two members his gang),Yuma Ansect and Haru glory make a cameo appearance.
 * The Demon Card member Bis appears as one of the members of Grimoire Heart and is defeated by Pantherlily. He had the Musica Sword, which was named after Musica's family.
 * In episode 126 of the Fairy Tail anime, a gang of thieves, known as the Jiggle Butt Gang appear. These thieves also appear in Rave Master.