For this you need to win a Sprite Slam Dunk Contest and then you need Kobe to step out to challenge you. The problem is that there is 6 possible outcomes to the dunk contest, and they are: Lebron James challenges you, Vince Carter challenges you, Jason Richardson challenges you, Tracy McGrady challenges you, Kobe Bryant challenges you, or nobody shows up at all. The best method to go about this is use the other 4 people(LBJ, VC, Tmac, and Richardson) in the dunk contest to eliminate those 4 outcomes. Keep trying and eventually Kobe will show up. To beat him the best method is: for the first dunk take off by doing a full rotation counter-clockwise and then in the air do another full rotation counter-clockwise. You will score 95-100. Then for the second dunk do the opposite, spin clockwise both times, and you will again score 95-100. The dunk-off is only 1 round, 2 dunks.