"Gagaga Caesar", "Gagaga Girl" and "Gagaga Clerk" in the artwork of "Gagagadraw".
"Gagaga" (ガガガ Gagaga) is an archetype used by the protagonist of the Yu-Gi-Oh! ZEXAL anime and manga, Yuma Tsukumo. The archetype is composed of four DARK Spellcaster-Type monsters and five EARTH Warrior-Type monsters, supported by an array of Spell and Trap Cards.
Their name, "Gagaga" is from either the pronunciation for the Chinese character they use as a crest, which can be pronounced "ga" in Japanese, or the Japanese manga sound effect "ga" which is used for physical impacts, similar to the English "pow" used in comics. This could be because the "Gagaga" monsters use physical attacks in the anime and manga. All "Gagaga" monsters bear a crest of the Chinese character for the first person pronoun (我) which can be pronounced "wa" or "ga" in Japanese. The crest cannot always be seen on the individual card's artwork though, but can be seen in the anime and manga, usually on the monsters' backs. The male members of the archetype cover the lower part of their faces with scarves, except "Gagaga Child".
The "Gagaga" Spellcasters, "Gagaga Magician" and "Gagaga Girl", bear a striking similarity in appearance to "Dark Magician" and "Dark Magician Girl" respectively, monsters used by Yugi Muto in the original anime and original manga. Both "Gagaga" Spellcasters are 3 Levels lower and possess 1000 less ATK than their "Dark Magician" counterparts. They are also all DARK Attribute monsters and are often used by Yuma and Yugi in their Duels. The "Gagaga" Spellcasters also share a "senpai and kohai" relationship, similar to how the "Dark Magicians" shared a master and apprentice relationship.
Despite being weak in terms of ATK and DEF, the effects of the "Gagaga" monsters allow them to change their Levels very easily, resulting in quick and easy Xyz Summons. The effect of "Gagaga Magician" allows him to change his Level from 1 through 8 and the effect of "Gagaga Girl" allows her to copy his Level. This allows them to easily Xyz Summon any generic, Spellcaster specific, or DARK Xyz Monster of Ranks 1 through 8. "Gagaga Caesar" also helps in this by using his effect to banish a monster in the Graveyard to change the Levels of all face-up "Gagaga" monsters you control to the banished monster's Level. This allows them to Xyz Summon any Xyz Monsters above Rank 8.
The greatest additions to the deck are Gagaga Child and Gagaga Sister. Child is capable of Special Summoning itself from the hand if one controls another "Gagaga" monster, fixing a lack of multiple summons for the deck, and then copy its level at the cost of the turn's Battle Phase, but this cost is mitigated by the strong monsters it can summon if used in conjunction with Gagaga Magician. For instance monsters like Evilswarm Exciton Knight, Number 101: Silent Honor ARK, Castel, the Skyblaster Musketeer, Maestroke the Symphony Djinn, Number 11: Big Eye, Divine Dragon Knight Felgrand to name a few, are more disruptive than offensive or have a battle related cost themselves, so they can be summoning affording the cost, with relatively small consequences. Sister when Normal Summoned can Search a "Gagaga" Spell or Trap Card, being capable of searching cards like Gagagashield or Gagagarush. Her true potential however lies on searching cards like Gagaga Academy Emergency Network and Gagagarevenge which can be used to Special Summon other "Gagaga" monsters, mainly Magician to use her own effect that targets another "Gagaga" monster, and makes the level of that monster and herself the sum of both, those granting access to very powerful monsters up to Rank 10, even without Magician since the other Gagaga monsters are Level 3 or 4, this equals to Rank 5 or 6 plays, which can be equally devastating.
Gagaga monsters however suffer from lack of speed. A good way to mitigate this is to combine Dododo monsters in the deck such as Dododo Warrior which has a high level and is easily used along Dododo Witch and Dododo Driver which can perform good combinations, with cards such as Onomatopaira that can search monsters key monsters such as "Gagaga Sister" or "Gagaga Magician" (the former is useful if one discards a Magician and searches a Sister to search a Gagagarevenge to Special Summon Magician), or cards like Dodododraw to draw 2 cards further increasing advantage.