Kim Jong Il denied his son succession rights because he tried to go to Disneyland!

North Korea tries really hard to stop any kind of outside pop-culture from coming into the country in fears that it would destabilize the dictatorship. The state-run media frequently claims that imperialists are trying to infiltrate the country through things like music and television. 

So when his son got caught with a fake passport trying to go to Tokyo Disneyland, Kim Jong Il took him out of the line of succession and put his younger son as the favored to replace him when he dies. The older son is up to his same tricks, however, as it was later reported that he let his own son go to the concert of South Korean superstar Rain

(Source)