"Gagaga Caesar", "Gagaga Girl" and "Gagaga Clerk".
"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 four 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 second series 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.