M. Night Shyamalan, a director with a sixth sense about young performers, auditioned “every child on this planet who was interested in acting and knew about martial arts” for “The Last Airbender.”

Or so it seemed, and then Paramount Pictures told him it planned to launch a website and invite hopefuls to post auditions to it.

“I was like, ‘Knock yourself out, this is never going to come to anything,’ ” he recalled with a laugh in a phone interview.

Thousands of would-be stars submitted their auditions, and hundreds of the most promising were sent to the Philadelphia filmmaker. Shyamalan whittled the field to the best 20 and then the top five, including a martial-arts champ from Dallas who filmed his audition in a basement.

“He’s really intriguing. He even shaved his head to do this part,” Shyamalan assumed.

He invited the boy, Noah Ringer, to join two professionals in auditioning in person.

“This kid has the right vibe. He’s really raw as an actor, but he’s got the right essence,” not to mention the fact that Noah was a ringer for the character of Aang in the animated TV series “Avatar: The Last Airbender.” The movie is based on the show.

“I think we should go with this kid, this total unknown,” Shyamalan suggested, “and lo and behold, the Internet got me the star.”

Like a director who hires an actor who can really play the piano for a musical role, Shyamalan opted for a 12-year-old in command of his body and the weapons he uses on-screen.

After enough people told Noah he looked like the cartoon character named Aang, he and his mother watched the show, and he fell in love with it and identified with the character.

“He worked so hard on his acting. I’m so proud, I love this kid and his family, too. They’re just the greatest, sweetest people you’ll meet,” Shyamalan said.

As for that hairless head, he didn’t do it for the audition but really shaves his head to keep cool during training (although he did paint a blue arrow to strengthen the Aang resemblance).

“This is a kid who’s home-schooled, like a monk, shaves his head like Aang, is totally into martial arts like Aang and has the kindest heart of a human being you’ll ever meet. He hangs out with my kids, and they’re like, ‘What most interests you?’ and he says, ‘Justice,’ and he’s not joking. He’s not joking.”

The world can weigh in on Shyamalan’s choice now that “The Last Airbender” has opened in theaters. It’s no longer “Avatar: The Last Airbender” because James Cameron also staked a claim to “Avatar,” and we all know how that turned out.

“One is the traditional, old-school meaning of ‘avatar,’ which is our movie, the embodiment of God-in-human-form kind of thing, and now you have the modern definition, which is a computer form of yourself,” Shyamalan said. “I guess after thinking of it that way, it was fine. We still had our title, and (Cameron) definitely had the title way before the cartoon show was made.”

In addition to young Ringer, the film stars Dev Patel, whom Shyamalan discovered before “Slumdog Millionaire”; Jackson Rathbone, best known as Jasper Hale from the “Twilight” series; Shaun Toub, memorable as the Persian store owner in “Crash”; and Cliff Curtis from “Whale Rider” and the TV series “Trauma.”

For those unfamiliar with the cartoon, just what is “The Last Airbender”? It’s an epic fantasy in 3-D (converted after filming) and the first of a hoped-for trilogy, set in a world with four nations known as Air, Fire, Earth and Water.

“Once in a generation, there’s an individual born who can manipulate all four elements. This is the Avatar. This person disappears, and a hundred years pass and the whole world has gone upside down,” Shyamalan said.

“The Fire nation has basically exterminated the Air nomads, and suddenly this boy is found in the ice ... and he has very little time to learn how to be this person that everyone needs him to be, before it’s too late.

“It’s meant to be an epic fantasy, for sure. It’s a very unusual movie in its tonality; it’s a mixture of fantasy and friendship and martial arts and philosophy.

“It’s full of Buddhism and Hinduism and reincarnation and heavy subjects underneath. There’s a cultural genocide that happens in the movie that’s at the center of the conflict, and then there’s such beautiful aspects.”

It boasts a “whole Shakespearean storyline” about a royal family gone bad and banished princes. Throw in the empowerment of a child, and Shyamalan was sold on the idea.

It was one of Shyamalan’s two daughters, in fact, who brought the TV show to his attention.

“She is now 10, and when she was 7, she was the first fan going crazy about it in my house, and, of course, in classic dad fashion, I didn’t pay attention to it. ... I’m like, ‘Yeah, yeah, yeah.’ ”

When they spotted the first season on DVD in a store, she begged her father to buy it, and the family watched it together.

“God, this is good, this is really interesting, and then we went upstairs. ... I turned around and said, ‘This would make a great movie.’ The whole house went crazy, screaming and yelling.”

Even the director’s wife told him, “This is exactly the perfect thing that you’ve been waiting for,” and it became his ninth movie.

“The Last Airbender” is far bigger than anything else the maker of “The Sixth Sense,” “Unbreakable,” “Signs” and “The Happening” has done.

“Easily 2 1/2 times. Two times is not even accurate. ... I can’t imagine how many people are in the end credits on this movie. It’s like a small city.”

The important July Fourth holiday box office is riding on “The Last Airbender,” which was the only big movie opening in the days before.

Asked about that pressure, Shyamalan said, “You know what? It’s fun. It was always meant to be this home-run swing, so it’s a very exciting thing. I think it’s a great honor to have that date for the movie, but when you see the movie’s personality ... it really fits that date.”