Happy is a blue, anthropomorphic cat alien from the planet Exceed, based on the character of the same title from Hiro Mashima's Fairy Tail series.

During Rebecca's childhood, he is killed in a roadside accident and revived in a mechanical body created by Professor Weisz. Acting as Rebecca's companion, he can reconfigure his body into a pair of rayguns called Happy Blasters, which Rebecca uses to fire non-lethal rounds of ether bullets.

(Source: Wikipedia)