Today (and tomorrow) is Day of the Dead, celebrated in Mexico and elsewhere. Sadly we don't go in for it much in the UK, because the artwork is really cool. It's not as creepy as it sounds: the idea is that you remember family and friends who have died. In many places it's traditional to visit graves and take offerings including flowers and the dead person's favourite food, and on the second day the spirits come to enjoy the gifts and festivities prepared for them. Sugar skulls are popular too, as gifts and tokens.
Like all festivals in parts of the world that aren't the UK and therefore rainy, there are parades and street parties and people gather to remember their dearly departed. The Day of the Dead is a national holiday in Mexico, so the whole day is one long celebration. And it is a celebration, not a sad day.
The name for the festival in Spanish is Dia de los Muertos (our name is a literal translation). Although it coincides with the Catholic festivals of All Saints' Day and All Souls' day, which is also about honouring the dead, it's an indigenous festival with its origins in Aztec worship of the goddess Mictecacihuatl (says Wikipedia).She's queen of the underworld (possible sacrificed as an infant) and these lovely ladies are catrinas, the modern representation of her. Apparently her jaws are often depicted agape because she swallows the stars during the day.
That tl sound at the end of the goddess's name is pretty common in Central American languages (like the language Nahuatl). It's on the end of the word for chocolate too, chocolatl - which is what Lyra calls it in the His Dark Materials trilogy. And it's pronounced something like the ll sound in Welsh.