The Pope will arrive in Cuba on Wednesday for the first time and will hold an open-air mass in the square next Saturday. While it was the President himself who allowed, even ordered, his image to be temporarily blotted out the symbolism should not be taken any further - the Pope is unlikely to reconvert Mr Castro to his childhood Catholicism. But could he nudge the long-time Communist leader towards democracy?
Few Cubans expect any public explosions of bottled-up Christian fervour to threaten his grip on power. But many hope the Pope's presence will bring greater religious freedom, embolden local critics of the one-party regime and encourage dialogue, both internally and with the US, which could pave the way for a peaceful transition.
As the Washington Post suggested last week, the Pope may play "good cop" to Washington's hardline anti-Castro "bad cop". "The Pope is in a position to offer concessions that an American government would have trouble making - and to reap concessions that the Cuban government could never make to the US."
In a late-night Friday TV broadcast, the Cuban leader insisted "we were not seeking to profit" by inviting the Pope, whom he described as "a very friendly man with a noble face." Many thought he was protesting too much.
If there was one outstanding reason to invite the head of the Catholic Church, it was surely to give world publicity to the Pope's support for a lifting of the US trade embargo, which has helped cripple the economy and is coming under increasing attack from Americans who see it as hurting the Cuban people, not the regime.
Some foreign commentators are tempted towards comparisons with the Pope's native Poland and his role in crushing communism there. But well under half Cuba's 11 million people are baptised Catholics, and most of those lost the habit of worship after Castro declared the island atheist in 1962. Most Cubans still support their leader, though more out of a kind of David-versus-Goliath patriotism than any lingering adherence to communism.
Also militating against major change is the fact that 60 per cent of Cubans are black, and tend to equate the Church with the white population, particularly the wealthy pre-revolution elite who mostly fled to Florida. In recent weeks, black cultural events have been encouraged, suggesting that the Cuban leader is using black sentiment as a counterweight to Catholic exuberance. He openly used the racial card in the early years of his revolution, warning that the white elite would again take over everything if they ever returned from Florida.
John Paul will also be aware that some 60 per cent of Cubans, including whites, believe to some extent in "black magic" religions brought from Africa, such as santeria, which involves trance-dancing and animal sacrifices. Hungry refugees who still flee Cuba aboard rafts often hold santeria ceremonies before putting to sea.
The Pope will no doubt have seen a poster, printed by Cuban exiles, showing the decomposing body of a 13-year-old girl who, along with her four-year- old sister, died of dehydration last year after their family fled on a leaky boat. The exiles mailed thousands of the posters to the Vatican and governments around the world. "Castro must be held accountable for his crimes against the Cuban people," it read.
Apart from devout Catholics, who simply want to see the Pope in person, most Cubans remain preoccupied with hunger. "If the Pope is bringing holy water to sprinkle on us, I'm not going to show up," said Jesus Rodriguez, a 32-year-old Havana carpenter. "If he brings cooking oil, we'll all be there." He was referring to the shortages and strict rationing in force since the collapse of the Soviet bloc, Cuba's longtime supporter and virtually the only supplier of most goods.
During his five-day visit to Havana and three other cities the Pope will see the effects of the US embargo at first hand: bicycles as the leading means of transport because of a lack of petrol, 1950s American cars patched up with home-made parts, people crammed aboard farm lorries to get between cities, the crumbling and flaking facades of the once-magnificent buildings along Havana's Malecon seafront. The jineteras (literally "jockeys", meaning prostitutes) will be kept out of sight by police, but were already jostling for position at the weekend in and around hotels packed with foreign journalists.
The regime has barred many journalists who have even vaguely criticised Castro in the past. No such problem for Martha Stewart, a popular US TV personality known for her food and how-to-do-things-about-the-house programme, who was given a visa as part of the CBS TV team. "I'm going to report on the foodstuffs available to the populace, and maybe the architecture," she said. She reportedly hopes to cook a meal for Mr Castro but, based on his past experiences of CIA assassination attempts, he is unlikely to partake unless she eats some first.
Such was the media circus already at the weekend that CNN was complaining it would be hard to compete with its mere staff of 85 - including its star reporter, Christiane Amanpour - while ABC, CBS and NBC had close on 200 personnel each, representing a significant dollar boost to the Cuban economy.
Many of the cameras will be pointed from the Malecon across the ocean on Saturday, when anti-Castro exiles are threatening to sail to Havana. "Castro can kill or imprison us, but we have a right as Cubans to enter our country to attend the Pope's Mass," said Ramon Saul Sanchez, leader of the Miami-based Democracy Movement. The US Coast Guard is under orders to stop them from entering Cuba's territorial waters, however, and Cuban patrol boats are unlikely to let the exiles pass.