The mariachi music style and band type originated in the Mexican state of Jalisco. Mariachi bands typically play trumpets, guitars, violins, and accordions, wear embroidered charro suits and sombreros, and traditionally show at Mexican weddings and plazas. One of their traditional functions of the mariachi is to serenade a woman.
Whenever a mariachi band shows up in fictional works, though, there is a tendency for them to pop up into a scene gratuitously. They are portrayed as obnoxious, with the loud trumpets that are typically part of mariachi bands are used to cement this. Mariachi bands are also portrayed as popping up in unlikely scenes to liven them up or to provide a dissonant tone (both musically and figuratively) to the situation. Therefore, this trope is usually seen in a comedy.
As a fun fact, mariachi bands run as far afield as Europe and China, so this trope isn't incredibly implausible.
Often a subtrope of Big-Lipped Alligator Moment. Very often a Non Sequitur. Often used for Rule of Funny or a Mood Dissonance. Can be portrayed as Dreadful Musician types. Incessant Music Madness can come into play.
- In Slipping Between Worlds, Ankh-Morpork in the Discworld has its version of the mass panic engendered by The War of the Worlds. As thousands pack the streets and panicked people flee into the surrounding countryside, strange things are indeed seen in the skies which acts, to the people, as bias confirmation. Meanwhile a mariachi band plays to a captive audience....
- Rango: The Mariachi Owls pop up throughout the movie, singing about the events of the story. They also function as a Greek Chorus.
- The SpongeBob SquarePants Movie: SpongeBob and Patrick are captured by a cyclops (actually a man in a diving suit) and taken to his gift shop to be dried and made into souvenir knickknacks. Among his victims are a group of fish made to look like a mariachi band. When the sprinkler system revives the fish, the mariachi band starts playing as they exact revenge on the cyclops.
- Planes: Dusty helps El Chu serenade Rochelle by bringing in a mariachi band to do a low-key version of "Love Machine" by The Miracles. Doubly impressive is the fact that they were in China at the time.
- In Ella Enchanted, the elven minstrels appear to be the local In-Universe equivalent, constantly popping up and singing to the protagonists at unwelcome times. In their defense, elves are forbidden from engaging in legitimate work, and are limited to either singing, dancing, or tomfoolery, so they have to make a living somehow.
- Mars Attacks! has the new president sworn in while a mariachi band plays the national anthem, serving to underscore just how vast the devastation was that no regular musicians were around.
- Bratz: Yasmin's family has a mariachi band that plays in their kitchen, which seems to just be an ordinary occurrence for them.
- The Naked Gun: In the second film Frank, Ed, Nordberg and Meinheimer use the costumes of a mariachi band to get into the Press Club Dinner - only to unintentionally walk onto a stage and have to give an impromptu performance of Besame Mucho to maintain their cover.
- Zookeeper: Griffin hired a mariachi band to impress Stephanie for his proposal, even though she rejected it.
- Star Trek: The Next Generation: The page image is from the end of "Deja Q". After spending the episode being Brought Down to Normal, Q has his powers restored by the Continuum, and he celebrates by bringing a mariachi band with him on the bridge of the USS Enterprise, much to Jean-Luc Picard's magisterial displeasure.
- Frasier: When Frasier is dared to fight a rival, he marvels at the media circus forming outside and quips that all that's missing is a mariachi band. Niles says "They're just setting up." When Frasier steps outside to face his opponent, the band starts playing.
- Arrested Development: One Running Gag is "The Sound Of Silence" playing when a character has an Oh, Crap! moment, at one point played by a passing mariachi band.
- Studio C has a sketch where Matt is celebrating the birthday of his coworker Whitney, and one of the many awkward gifts he attempts to give her is a mariachi band that pops up and starts playing music.
- Brooklyn Nine-Nine: During the Cinco de Mayo heist, Jake and Terry hire the same mariachi band to play during supposedly epic moments.
- In one appearance on The Graham Norton Show, Salma Hayek talks about someone hiring a mariachi band for her fiftieth birthday. While she appreciated the gesture, Salma still decided to break the person's ovaries.
- Ninja Sex Party: In "Eating Food In The Shower", Danny had hired a mariachi band to play while he and his date were having dinner in the shower. In the video, this only lead to extra chaos and limited space.
- In the music video for Train's "50 Ways to Say Goodbye," as the lead singer Patrick Monahan begins to make excuses to David Hasselhoff why Monahan's girlfriend isn't around. As he breaks into song listing excuses, a mariachi band suddenly appears in the supermarket to back his vocals.
- John Mulaney has a bit about obnoxious mariachi bands he has encountered in the subway.
I don't know what it's like in the moments just before you're killed by hitmen, but I bet it's not unlike when you're on the subway and you realize a mariachi band is about to start playing. (Off-key singing) Oh-da-la-low-de-por-arl! THIS IS THE LOUDEST THING IN THE WORLD!
- Sam & Max: Freelance Police: In Season Two, about Once an Episode, someone will mention a birthday, causing a mariachi player to come out of nowhere and say "Did somebody say "birthday?", play some music, and then leave. Later in the season, it's revealed that the mariachi players are actually the same man from different points in time, who made a Deal with the Devil to keep playing his music in exchange for working for Satan, sending damned souls to hell.
- In Paper Mario: Sticker Star, one can find Sombrero-wearing Shy-Guys playing the guitar through World 2. Which is a very Egyptian desert. There is even a full mariachi band consisting of one Sombrero Guy, an Accordion Guy and a Maraca Guy playing on a sphinx.
- Earthbound and MOTHER 3 both have gratuitous mariachi slot machine men, Pincho, Pancho, and Tomas Jefferson. They are dressed up as both mariachis and slot machines. They let you play them as if they were slot machines.
- Chavo Guerrero Jr.: His championship celebration after winning the WWE ECW Heavyweight Title had a mariachi band in the ring play - only for the band leader to turn around and break a guitar over his head before revealing himself as CM Punk
- Brock Lesnar had demonstrated to have funny and unsettling moments. One of the most famous ones was in 2004 when he had a feud with Eddie Guerrero and in a SmackDown show he entered with a entire mariachi band and a giant Mexican sombrero making a celebration, when Guerrero came later to end it.
- Spongebob Squarepants: After watching the Lost Episode, Patchy the Pirate wants to watch it again. But since he doesn't know how to work the remote, Patchy surfs through other channels, until Potty tries to grab it and they accidentally press the mariachi button.
Patchy: I HATE TECHNOLOGYYYYY!!!
- ¡Mucha Lucha!: The episode, "The Musica Man" featured Masked Luchador mariachis that Rikochet hired to play for his signature entrance. They get obnoxious later in the episode. Mariachis and lucha libre are both Mexican, but they are not usually paired together.
- My Little Pony: Friendship Is Magic: "Inspiration Manifestation" has an inversion. While Rarity is going mad due to the power of a new Reality Warper spell, she decides to bring a child's birthday party up to her own standards of beauty—which includes transforming the hired mariachi band into a classical music ensemble. In other words not-gratuitous mariachi getting replaced by gratuitous classical music.
- Phineas and Ferb: "One Good Scare Ought To Do It" has the Mariachi Tree. Which is a mariachi band, but on a tree. The brothers move on to another plan for the day when the band falls from the tree.
- In one episode of Hi Hi Puffy AmiYumi, the titular duo are forced to fight a bull. They naturally try to escape the night before but each of their attempts are interrupted by a mariachi band.
- The Loud House episode "Save The Date", semi-justified by the fact that part of the episode takes place at a Mexican/French restaurant. It plays up the "obnoxious" aspect as Lincoln keeps bumping into the band, who get out only a few notes before Lincoln either scolds them or walks away. They serve as The Tag to the episode when Clyde cues them up at school the following day.
- King of the Hill: Naturally they show up when the cast vacation in Mexico when Hank and Khan stop at a bar, trying to get Hank to throw some money their way to get them to stop. Hank directs them to Khan who fights back by singing, managing to scare them off when he sings "She Blinded Me With Science".