(NYTIMES) - Eight months after introducing the world to Luke Skywalker, Princess Leia and Chewbacca, George Lucas invited Steven Spielberg and screenwriter Lawrence Kasdan to his assistant's home in Los Angeles to pitch a new name for adventure.

That brainstorming session led to Raiders Of The Lost Ark, which celebrates its 40th anniversary this month.

Four decades later, the hit has become the pivot point between cinema's past and present.

Indiana Jones' narrow escapes from Nazis, boulders, blow darts, poisoned dates, speeding trucks and, of course, snakes, tip a fedora to the cliffhanger serials of the 1930s - the kiddie adventures that shaped his creators - even as they calibrated their nostalgia into a cross-promotional blockbuster that would define Hollywood's future.

"What we're just doing here, really, is designing a ride at Disneyland," Spielberg said at that first meeting.

Prophetic words. Yet, like Indy's exploits around the globe, the film's production history is itself a tale of misadventure, lucky breaks and inspiration.

Here are four secret stories from the set.

1. Spielberg's impractical commitment to practical effects

The film's set pieces, from locations to traps, are temples of old Hollywood craftsmanship.

Indy's seaplane departure, the snowbound Nepalese saloon and the plummeting cliffs of Cairo were all handmade matt paintings.

On average, a matt painting has only a few seconds before the audience catches on to the trick.

Yet, the sprawling warehouse in the film's final shot had to command the screen for nearly half a minute and took the artist Michael Pangrazio three months to complete.

2. The desert shoot destroyed morale

During the worst stretch of filming on location in Tunisia, the crew must have wished the entire Egypt sequence could have been hand-painted. Temperatures clawed to around 54 deg C and everyone but Spielberg was waylaid by food poisoning. Spielberg packed a crate of canned food, which he ate for breakfast, lunch and dinner, often cold.

Their suffering excuses the continuity errors in the Well of Souls sequence, where bricks, rocks and even a truck shift restlessly in the frame as though they, too, are anxious for an iced tea by the hotel pool.

The most egregious blooper occurs when Indy and old flame Marion (Karen Allen) burst through the Well of Souls less than 1m from what appears to be an unconscious man in a blue shirt.

The man is a vestige from either a deleted fight scene or a failed gag in which a worker is so startled to see living bodies exhumed from a 1,000-year-old sealed tomb that he faints dead.

The mystery of his origins is matched by a second question: Why is a 1,000-year-old sealed tomb covered in construction scaffolding?

3. Indy's weakness became his strength

Alas, star Harrison Ford, too, was stricken with dysentery when it came time to shoot an epic sword-versus-whip duel for which Spielberg had budgeted 1½ days of filming, according to the 1996 biography Spielberg: The Man, The Movies, The Mythology.

Ford asked if they could wrap the scene in an hour. "Yeah, if you shoot him," Spielberg joked.

So they did, and the wordless punchline got one of the film's biggest laughs.

4. Animal antics

Also improvised were the animal performances, a natural by-product of casting snakes and tarantulas instead of golden retrievers.

Apart from a few nips at the calves of the animal handler Steve Edge, who shaved his legs to double as actress Allen, the snakes - all 6,500 of them - mostly behaved themselves, so much that Spielberg, when anxious, could cradle one in his hands like a rosary.

Not the treacherous capuchin monkey, which, despite being trained to perform a Nazi salute, squandered 50 takes before an exasperated Lucas, handling the insert shot, dangled a grape on a fishing line.