Answer:
   
   At the time of the Spanish Inquisition and the expulsion from Spain in
   1492, Jews were offered conversion or expulsion. Many chose to leave
   Spain (quite a few found safety in the Muslim Ottoman Empire), but
   others stayed behind.
   
   "Marranos" actually started appearing with the first riots in the
   Juderias of Spain. Many were forced to convert to save their lives.
   These were naturally not faithful Catholics. The laws in 14th and 15th
   century Spain became increasingly oppressive towards practicing Jews,
   while providing an easy escape by conversion. Large numbers of middle
   class Jews outwardly took on Christianity to avoid the laws, while
   secretly practicing Judaism. [The term Marrano appears to be derived
   from the color of the robes of a Roman Catholic Bishop; Jews who
   converted were placed under the direct tutelage of that bishop. One
   source indicates that the term "marrano" means pig literally in
   Spanish, and notes that the converted Jews were called that because
   one of the ideals of the Spanish society in the times of the Catholic
   Kings was purity of blood--hence, if a person couldn't prove to be
   totally "clean" of blood (i.e., that they were a descendant of
   Christian Spaniards), they were called a marrano.]
   
   Most of the remaining Marranic practice in Spain and Portugal today is
   from those religious Jews who escaped from Spain to Portugal in 1492,
   only to be trapped there later when the expulsion was instituted there
   as well. The most active Marranism in the Iberian peninsula is in the
   mountainous border areas between Spain and Portugal, in towns such as
   Belmonte'. Jewish outreach in these areas is achieving success in
   bringing them forward and restoring full Judaic practice, but many
   still fear burning or other persecution if they go public.
   
   Some faithful Catholic converts were won by the efforts of famous
   apostates like Pablo de Santa Maria who went around disputing the
   rabbis and ordinary Jews, winning some converts. In the most famous
   disputation, with Nachmanides, he was soundly defeated, but the
   Franciscans published false reports of the disputation to win more
   converts. Nachmanides, who had been protected from heresy laws during
   the disputations, was forced to publish his refutations in public. He
   was forced into exile rather than be burned as a heretic. In any case,
   the faithfulness of these converts is doubtful, since the Order of
   Expulsion was primarily due to the recidivism of Conversos once they
   had to live next door to practicing Jews again. It was felt that
   expelling all open Jews was the only way to keep the Conversos
   Christian.
   
   Among those who stayed behind were Jews who pretended to convert to
   Roman Catholicism, but who secretly maintained a practice of Judaism.
   The term "Marrano" was at one time used to describe them, as the term
   refers to the swine which they'd publicly eat to demonstrate their
   outward conversion. It isn't clear if the "Old Christians" or the
   practicing Jews called them "marrano".
   
   In Majorca the community was converted in the 1430's and are called
   Chuetas, from "pork lard" since they regularly keep pork lard boiling
   in cauldrons on their porches. They themselves still call themselves
   Israelitas in private, and ask forgiveness from el Grande Dio for
   worshipping in front of statues of a man. They typically sacrified (in
   a figurative, not literal, sense) their first born sons to the
   Catholic priesthood as a means of getting protection from Church
   persecution, so, ironically, many of the priests across the Baleiric
   Islands are from Marrano families.
   
   Crypto-Jew is the correct term, as it also refers to Jews forced to
   adopt other religions and political philosophies while maintaining
   Jewish practices. Crypto-Judaism pre-dates the Inquisition, as Jews
   were forced by the Al-Mohavid invasions of Spain to become Muslims,
   creating Crypto-Jews who gradually fled to Christian districts for
   protection from the Muslims (see Roth's History of the Jews). In
   modern times outwardly Muslim Crypto-Jews are known to be in Meshed,
   Iran, and in Turkey.
   
   A number of Crypto-Jewish communities survive today, especially in
   former Spanish-influenced regions, such as the southwestern U.S.A.
   They still maintain extensive secrecy after centuries. Other
   communities were lost to assimilation, but maintained residual Jewish
   practices such as lighting candles Friday night. Cohen's The Marranos
   and Prinz's The Secret Jews claim that the following are examples of
   such communities, although such claims have not been verified and are
   disputed by some:
     * The Antiqueñas of Colombia.
     * Much of Northern Mexico's middle and upper classes (Nuevo Leon is
       the "New Lion of Judah"). Note: Some note that Neuvo Leon mean was
       named after the old Leon in Spain. However, whatever the origin of
       the name, many of the families of Monterrey, Nuevo Leon, have
       managed to keep in their memory, after more than 400 years, their
       Separdic origin.
     * The Naucalpan and Vallejo districts of Mexico City. (Technically,
       Naucalpan is not in the Distrito Federal, but in the greater
       metropolitan area).
     * The Chuetas of Majorca. A look at Chueta last names shows many
       surnames which have became quite famous in the Hispanic world.
       They include Mir, Miro, and Marti. Of course Joan Miro was
       Mallorcan. Any marranism in Fidel Castro's family would be through
       his mother, as his father's family was Gallego, and very few Jews
       ever lived in Galicia (of course plenty lived in the Austrian
       Galicia, I'm refering to northwestern Spain ). Interesting about
       the mountains on the Spanish-Portuguese border being a hotbed of
       marranism, particularly those on the Extremadura-Andalucia border.
       This area is directly inland from some of the areas which
       contained the earliest Jewish communities on the Iberian peninsula
       - for example Huelva and Gibraltar. Malaga and Almunecar - which
       also had early communities - are also in Andalucia. According to
       Timothy Mitchell's book Flamenco: Deep Song and other sources, the
       inquisition in western Andalucia was slightly more lenient than
       elsewhere because of the need for labour related for the new world
       trade and mining. The connections are quite interesting.
       
   Famous Hispanics who have acknowledged Marrano ancestry include Rita
   Moreno and Fidel Castro. Jews have played an important role in the
   history of Monterrey, Mexico. Frida Kahlo's father, Guillermo Kahlo, a
   somewhat reknowned photographer in his own right, was a Hungarian Jew.