“Brazilians celebrate the day before Lent with dancing samba in skimpy outfits. In New Orleans, revelers throw beads at Mardi Gras. In this dusty central Mexican town, they have a different kind of a blast. … Even amid the inexhaustible tally of quirky rituals that communities anywhere hold dear, the Fat Tuesday frenzy in San Juan de la Vega elicits awe.”