Brazil, Italy, Trinidad and Tobago — these are the places I think of for Carnival. I did not really think of a little town outside Oaxaca, Mexico where devils take to the streets and people don animal skulls, clanging bells and covering themselves in motor oil. And yet, this year on Fat Tuesday (the final day before Lent begins), that is exactly where I found myself. 
Preparations
San Martin Tijacete is about 40 minutes outside of Oaxaca City, in a valley known for its artisans. This event is called Carnaval Ancestral, as it's not just regular Carnival: it's a blend of the Catholic tradition and the village's local traditions. In a town so close to Oaxaca City, where Day of the Dead is the pinnacle event of the year, it's no surprise that painting your face up like a skull is completely normal. Don't ask about the dinosaur - my Spanish is good, but not *that* good.
Skulls and bells
Two major aspects of this event are wearing skulls (or terrifying masks) and clanging bells. I was told that this was to scare away bad spirits before the season of Lent (40ish days of fasting before Easter) by one person, and told it was to personify sins and sinful human nature by another. I expect both answers are true.
Say "cheese"!
Two boys ready to go.
Intermission
Ready to go
Children wait in their doorway, ready to hit the streets and get to screaming and rattling and wreaking havoc.
Bands of color
There was the black and horned band, the yellow and blue band, the full silver band, and more. Others head out solo, while some cross-dress, don skulls, or wear the traditional Albrejie masks the town is known for. Many had cowbells tied to them, reaching back and ringing them out at every turn.
Yellow and Silver
Whatever they're putting on their skin, it's strong. But it's worth it for the pop of color. The boys around this age seemed particularly invested in the parade and participation.
Teens are the same everywhere
Adjusting his hair time and time again, so it was just right. The universal teenager, ladies and gentlemen.
Take to the streets
This day begins around 8 AM when there is a public breakfast and life tumbles out into the streets. By 11 AM there are large crowds, ready for the traditional parade down the street.
Gather
As the parade commences, some are wearing devil costumes and masks to ward off evil spirits and cleanse the town for Lent while some wear hand-painted wooden masks instead, as the town is famous for wood carvings called Albrejie. Alongside the howling devils, there is a couple dressed as if for a wedding, whom the crowd marches to the Major's house where a fake civil ceremony is performed.
Welcome
It was mesmerizing, unnerving, and magical.
Masks and mayhem
Left is a traditional Albrejie mask. San Martin Tilacete is famous for its work with copal wood, making fantastical animals, masks, and anthropomorphic carvings. If you saw the movie "Coco," the wild pink dog was an Albrejie brought to life. To the right, three rogue boys come shouting down the side street to join the fun.
Intermission
Say "cheese", please
All day long, the locals paused and posed for the many photographers present; it almost felt like part of the fun. They were very proud of their special carnival and of the costumes they worked hard on. That said, the town must find itself a bit of tension: wanting the tourism and the pride of showing off such a unique tradition, but not wanting to compromise the tradition itself. For example, a band of 6 or 7 tourists had been painted up and joined in the parade, toting Dos Equis beers as they went. I have no doubt they were invited by locals - and honestly, welcomed into the parade warmly, it seemed - but I did find it a red flag that the tradition might be on the brink to some extent of losing something. I was unable to confirm there was any issue with the tourists joining, but as I watched the tipsy visitors happily dance and shout in skin paint and grass skirts, I wondered what it might mean. (An English-speaking local next to me quipped "I wonder if they got lost trying to find Burning Man?")
Horns, horns, horns
It didn't get old.
Smile, girls
While I couldn't figure out why, it did appear that cross-dressing was part of this event for some. My guess would be to confuse the devils, or to just let it all out before Lent.
Costume contest
Later in the day, the town regrouped in the center for a large costume contest. The rowdy nature built up as the night went on. Someone was crowned King and Queen of the day, and I am pretty sure someone won a horse. This little girl is proof you don't have to dress up terrifying - almost any costume is acceptable.
The band plays on
A band that had marched along with the crowd lined up to play on for the costume contest. A tuba, a horn section, a drummer, and a singer were all on hand.
That's a wrap
Once the winners were announced, the event just turned into a huge cross-dressing, horn-wearing, mask-clad, undulating party. Everyone stayed out late, and then I assume made futile attempts to shower. Good luck - I got smeared with the black "'paint" and it was 100% motor oil. Six days later, I still have it all over my face and arms - it's an unpleasant but welcome reminder of this wonderful, odd, unique event over in San Martin Tilcajete.