In 1979, October in Key West meant the dog days of a late subtropical summer. Some streets were so empty that dogs could actually be spotted dozing on the asphalt.

But a group of local merchants changed that when they conceived a novel way to mark Halloween, a favorite island holiday that residents celebrated with uninhibited flair: a Halloween festival they dubbed Fantasy Fest.

Revelers costumed as space creatures "invaded" Key West during a previous Fantasy Fest. (Photo by Rob O'Neal, Florida Keys News Bureau)

Revelers costumed as space creatures “invaded” Key West during a previous Fantasy Fest. (Photo by Rob O’Neal, Florida Keys News Bureau)

Their 1979 event was a two-day party featuring a food fair and a parade — the latter distinguished by the appearance of a local woman called Sister, who draped her nude metallic-painted body across the hood of a Lincoln Continental and proclaimed herself its hood ornament.

After that auspicious beginning, the festival became an annual extravaganza known as the perfect place to “let it all hang out.” Organizers promoted it nationwide, and visitors began flocking to Key West each October.

Eventually it grew to 10 days. National and international media — including famed television weatherman Willard Scott — lauded its often risqué costume competitions, lavish masquerade balls and grand parade that featured fabulous floats and marching groups in bright-colored finery.

In the mid-1990s Willard made an on-air statement that some locals still remember. Displaying an elaborate feathered Fantasy Fest mask live on “The Today Show,” he enthusiastically blurted, “And in Key West this week, they’re having their annual Fanny Fest!”

Whatever you call the festival, most residents can recall an offbeat Fantasy Fest incident or two. Like the night a “spaceman” had dire technical difficulties with his flying saucer outside Sloppy Joe’s Bar. Or the year half-naked “headhunters” rampaged up Duval Street in wild abandon.

Diana Nyad Key West Fantasy Fest

Endurance swimmer Diana Nyad, the first person to swim from Cuba to Key West without a shark cage, was honored as grand marshal of a past Fantasy Fest Parade. (Photo by Andy Newman, Florida Keys News Bureau)

Yet despite its outrageous flavor, Fantasy Fest also has a more serious side.

In 2013, for example, the grand marshal of its highlight parade was endurance athlete Diana Nyad — just seven weeks after she completed a grueling 53-hour, 111-mile swim from Cuba to Key West without a shark cage.

When she successfully finished her record-setting swim, triumphing on her fifth attempt at the Florida Straits crossing, nearly 2,000 people greeted her with loud cheers and applause. During the Fantasy Fest parade, however, some 60,000 spectators celebrated her accomplishment.

Diana rode on a float commemorating her historic arrival near Key West’s landmark Southernmost Point marker, surrounded by marchers dressed as jellyfish with trailing tentacles.

Perhaps the most poignant moment in Fantasy Fest history came in 2001. Just weeks after the Sept. 11 terrorist attacks, the festival gave eight exhausted, grieving New York City firefighters a chance to relax and smile.

Months before, firefighters Michael Carlo and his brother Rob, teammates on the 10-member FDNY volleyball team, had decided to march in the year’s Fantasy Fest parade. But their plans — and their lives — were shattered when the World Trade Center’s twin towers collapsed.

FDNY Fantasy Fest Key West

A group of New York firefighters honored their fallen comrades in the Fantasy Fest Parade shortly after the Sept. 11 terrorist attacks. (Photo by Andy Newman, Florida Keys News Bureau)

Mike Carlo died in the rubble, as did volleyball team member Tim Welty. The remaining eight teammates, though devastated by their loss, put in heartbreaking weeks working at Ground Zero.

But the night of the 2001 Fantasy Fest parade, dressed in red, white and blue T-shirts bearing Mike and Tim’s names, they marched the length of the parade route in memory of their lost brothers.

Rob carried Mike’s photograph, while a teammate waved a sign that read, “FDNY — Still the Greatest Job on Earth.” An estimated 50,000 spectators cheered, blinked back tears, and chanted “USA! USA!” as the firefighters passed by.

Fantasy Fest 2016 began Oct. 21 and runs through Sunday, Oct. 30, with the parade set for Saturday night. Since that’s just days before the hotly-contested U.S. presidential election, festival organizers expect many parade floats and costumes to feature a political focus — spiced with the good-spirited flamboyance that characterizes Fantasy Fest and Key West itself.