Thread pork pieces, pineapple, and pepper on 24 toothpicks. In a medium saute pan, mix pineapple juice, soy sauce, brown sugar, and ginger. Bring to a boil over medium heat; add kabobs to pan, cover, and cook 2 to 3 minutes. Uncover and cook 2 minutes more, until pork is cooked through; turn kabobs occasionally to coat. Remove toothpicks before serving.