Both as a spy and a film-series brand, James Bond is invincible.

The franchise, celebrating its 50th anniversary with this week's U.S. release of "Skyfall," is the longest-lived in movie history. Adjusting for inflation, it's also the most lucrative.

The Bond formula of exotic locales, exquisite women, elegant tailoring and extreme danger spawned scads of imitators, but outlasted them all through sheer evolutionary agility. The films regained their youth and topicality with each new leading man, from "Dr. No's" echoes of the Cuban missile crisis to "Skyfall's" cyber-terrorism. That potent cocktail of old and new enables Bond to span a multitude of periods, locales and adversaries. Jason Bourne, John McClane or Ethan Hunt could never fit as smoothly in 1962 Jamaica and 2012 Shanghai.

Bond's wide appeal began with Ian Fleming's Cold War spy novels, which cast his hero as a lethal mix of British gentleman and blunt instrument. Cary Grant was approached to take the role. Fleming was displeased when Sean Connery was cast, calling him "an overdeveloped stunt man." But as audiences embraced Connery, the novelist was won over. In later books, Fleming even gave 007 a partly Scots ancestry.

In the years since, Bond has matured from a gadget-equipped action figure to a three-dimensional character. M has morphed from Bernard Lee to Judi Dench. The more times change, the more the iconic spy endures. Though his monomaniacal enemies hoped to control the world, it's Bond who achieved global domination.