At the tail end of 2014, Danilo Maldonado Machado, the graffiti artist known as “El Sexto,” was detained by the authorities as he made his way to a public park in Havana to stage a work of protest art. In his vehicle, he was carrying a pair of pigs that he had painted with the names of the Castro brothers — one “Raul,” the other “Fidel.” His plan was to release them and let members of the public catch them and take them home.