The man who will have his pudgy finger on North Korea’s nuclear button is an overweight comic-book freak who is crazy about James Bond, Jean-Claude Van Damme and Jackie Chan movies, and who dreamed about following his hero Michael Jordan into the NBA.

Kim Jong Un, the handpicked “Great Successor” to Kim Jong Il, who died Sunday, is an unlikely addition to the ranks of the world’s leaders. He had no known political, diplomatic or military experience before his father made him a four-star general last year and anointed him as crown prince of the world’s only communist dynasty.

Much about Jong Un remains a state secret, including his age — speculation centers on 27 or 28 — the identity of his mother and his own marital status.

Former US envoy Bill Richardson, who has visited Pyongyang, said the power vacuum created by his father’s death raises “extreme concern because North Korea and the peninsula is a tinderbox.”

He said the next 24 hours would determine how firmly Kim Jong Un is in control. That’s important because North Korea is believed to have enough plutonium for eight atomic bombs.

The Obama administration greeted Kim Jong Il’s death cautiously. President Obama spoke with South Korean President Lee Myung-bak shortly after the news broke, and officials said US diplomats were also in close contact with Japan, which always watches Pyongyang nervously.

White House spokesman Jay Carney told reporters, “We hope that the new North Korean leadership will take the steps necessary to support peace, prosperity and a better future for the North Korean people, including . . . acting on its commitments to denuclearization.”

Apart from a short-range missile test — which may have been previously scheduled by North Korea — the border area remained quiet.

Kim Jong Un is the youngest of three sons of a bizarrely dysfunctional family. His older brother Kim Jong Nam apparently lost his chance to succeed Kim Jong Il after he was caught in 2001 trying to sneak into Japan — using a bogus Dominican Republic passport — to visit the Tokyo version of Disneyland. Another brother, Kim Jong Chol, was said to have been ruled out of the succession race because he is “too effeminate.”

Kim Jong Un is known to speak English, German and French that he picked up in a Swiss boarding school, which he attended under an alias.

Classmates said he was quiet and seemed to be shy or sullen and uncomfortable with women.

They said he is an avid skier, a devoted reader of Japanese manga comics, an avid computer-game player, and fanatical about basketball — particularly the fortunes of the Chicago Bulls.

“He yearned to become a pro basketball player in the United States,” a former schoolmate at the International School of Bern told Japan’s NHK TV network.

But his hoop dreams were doomed by extra pounds, apparently due to lack of exercise and diabetes, as well as high blood pressure and what are believed to be the effects of a car accident.

His name was virtually a national secret until September 2010, when his father named him to several top government posts, including making him a member of the powerful Central Military Commission.

The state propaganda machine called him the “Young General” and the “Brilliant Comrade” and later the “Respected General,” before he was elevated, by his father’s death, to “Great Successor.”

The government also promoted a song, “Footsteps,” which appears to refer to his role in carrying on his family’s legacy. There were also hints that he was computer-savvy, when the heavy-handed state media repeatedly aired “Song of CNC,” or Computerized Numerical Control, better known elsewhere as digital technology.

But like his father, a former playboy who remained in obscurity for years as he was groomed for the top spot, much about Jong Un remains a mystery.

“There is a rumor that he is married, but officially we don’t know,” said Yoon Deok-ryong, of the Korea Institute for International Economic Policy in Seoul, South Korea. Jong Un’s mother is believed to have been a Japanese-born dancer who died several years ago. But nobody knows for sure.

One of the very few outsiders to get to know the “Great Successor” is Kim Jong Il’s sushi chef, Kenji Fujimoto, who has been in hiding, fearing execution by North Korean assassins since he fled. He described Jong Un as “a chip off the old block, a spitting image of his father in terms of face, body shape and personality.”

The chef said when he first met the boy he was dressed in a military uniform, and he “glared at me with a menacing look when we shook hands.” Fujimoto added, “I can never forget the look in his eyes, which seemed to be saying, ‘This one is a despicable Japanese.’ ”

As he was elevated, a wider audience has come to know Jong Un as a fearsome figure.

After he gave his good wishes to North Korea’s national soccer team last year — and the team lost all three World Cup matches — the members were forced to stand outside the People’s Palace of Culture in Pyongyang and be denounced by students and fellow athletes because they had betrayed the heir apparent.