In a study of more than 3,000 men, no correlation was found between the self-reported size of feet and that of the crown jewels. Skeptical of a man's ability to size himself up, some researchers have, well, taken things into their own hands.
For example, a 2002 study, headed by Jyoti Shah at St. Mary's Hospital in London, compared foot size to carefully measured privates (all 104 penises were stretched to their longest length for consistency.) No correlation was found.