There is no musical outfit more annoying than the mariachi band. (Sorry, mariachi band members, but it's true.) They're enjoyable for all of about 45 seconds when they make their way to your table at a Mexican restaurant, but after that, it's adios.
This is also what makes them ideal for pranks. Seniors at Santa Barbara High School hired a mariachi band to follow their principal around for the day, trolling him with the sounds of classical Spanish guitar and trumpet -- starting promptly at 7:30 in the morning.