So which prince was running in the Brazilian heat?
Prince Harry goofily donned a mask of his brother Prince Williamas he took part in a mile-long fun-run Saturday.
He was given it by another runner among a group who'd decided to don royal masks, and he flipped it on during the six-minute run.
The unplanned moment, which an aide said would give his brother a "laugh," came during the first event of a sporty morning on the Praia do Flamengo beach, in the shadow of Rio de Janeiro's magnificent Sugar Loaf Mountain.
After a visit to Jamaica, Harry, 27, is in Brazil to highlight British interests and support his charitable causes.
On Friday night, he was welcomed by a samba band and then boarded a cable car to the top of Sugar Loaf to attend a party with Brazilian celebrities and politicians.
"Everything about Rio makes you want to dance," he said. He added: "I'm just glad my brother isn't here, because he might do it, and that would not be cool."