California lucha libre veteran of many years who achieved national fame when he debuted on Lucha Underground's 3rd episode as a restaurant worker from down the street recruited by Dario Cueto to fight back against complaints about the lack of Mexican luchadors on the show. Cuetro promised Mariachi would sing a song if he won; Mariachi has never won. Mariachi makes up for it by dancing during his matches. Mariachi Loco is much more successful on the indies, expanding out to Arizona indies in 2015.
Improbably, there's also a Mariachi Loco in Texas, who's completely unrelated.