The comandante's appearance at the Latin American summit in Cartagena, Colombia, this week wearing a white guayabera shirt has Cuba-watchers in a tizzy. It was the first time anyone could remember him appearing at a formal occasion without his trademark olive uniform and matching cap.
A guayabera is a dressy tropical shirt worn outside the trousers to allow air to flow around the torso.
The valet theory was dismissed. The Cuban leader has more than one uniform. After all, he travels with a second decoy aircraft and takes his own water, food and bedsheets in case the CIA, try to finish him off again. No-one could imagine a Colombian hotel staffer tapping on Mr Castro's door with a 'terribly sorry, comandante, there was a slight accident with your jacket. Would you like to borrow a guayabera?' No, Fidel was giving the world a message. But what?
For students of the enigmatic revolutionary leader, it was as puzzling as working out the pecking order of Red Square parades in the days of the Cold War To some, the shedding of the uniform was like the fall of the Berlin wall. Mr Castro was telling the world he was prepared to open up to capitalism. What of the pistol? There was no bulge beneath the guayabera as he stood for the snapshot with other heads of state.
'Fidel, it's you, I didn't recognise you]' the Spanish Prime Minister, Felipe Gonzalez, is said to have joked.