Who stole JFK's brain? It has been a mystery since 1966 when, three years after the president's assassination, it was discovered that his brain, which had been removed during the autopsy and stored in the National Archives, had gone missing. Conspiracy theorists have long suggested the missing organ would have proved Kennedy was not shot from the back by Lee Harvey Oswald, but from the front.

The latest theory puts forward a less juicy cover-up – James Swanson, author of a new book on the assassination of Kennedy, suggests the president's brain was taken by his younger brother Robert, "perhaps to conceal evidence of the true extent of President Kennedy's illnesses, or perhaps to conceal evidence of the number of medications that President Kennedy was taking".

Kennedy is just one of a number of famous people whose body parts were taken, either for good or dubious purposes. Brains have long held a fascination, particularly for people wanting to study the secrets of the intelligent, talented and powerful. After Albert Einstein's death in 1955, his brain was removed and studied by pathologist Thomas Harvey, much of it sliced and mounted on hundreds of slides, many of which have been lost. The Moscow Brain Institute collected and studied the brains of many prominent Russian scientists and thinkers, most famously that of Lenin.

Joseph Haydn's head was stolen from his grave by two men, motivated by their interest in phrenology, the belief that insights could be had from feeling the shape and size of the head, the skull eventually finding its way to the Society of the Friends of Music in Vienna, more than 80 years after his death. It was reunited with the rest of his remains in 1954. When Beethoven died several years after Haydn, and with the interest in phrenology still booming, there were similar concerns, with one gravedigger claiming he had been offered a thousand florins to "deposit the head of Beethoven in a certain place". However, the composer didn't escape unscathed – during his autopsy, one doctor took his ear bones, locks of hair were clipped, and when his body was exhumed later in the 1800s, fragments of his skull were taken.

What is reputed to be Mozart's skull – tests have been inconclusive – is held at the International Mozarteum Foundation in Salzburg; it is his skeleton that is missing, since he was buried in a grave that was dug up and reused some years after his death in 1791. Thomas Paine's remains are also lost. In 1819, 10 years after the pamphleteer's death in New York, the journalist William Cobbett brought his bones back to England, with the idea that he would be interred in an impressive tomb, though this never happened; people all over the world have claimed to own a part of Paine. Napoleon's body parts are also thought to be scattered – intestines allegedly belonging to him were held in London and destroyed during a bombing raid during the blitz, but his penis is believed to be owned by the daughter of John Lattimer, a New Jersey urologist (he was also the doctor brought in by the Kennedy family to review JFK's autopsy evidence) who bought it at an auction in 1977.

In some cases, remains turn up years later. In 2009, two of Galileo's fingers and a tooth were rediscovered. Removed by admirers, rather like holy relics, 95 years after the astronomer's death, they had last been seen in 1905 before resurfacing and being brought to the Museum of the History of Science in Florence. The museum, now called the Galileo Museum, was already home to another of Galileo's fingers.