How to Make It
Line a plate with paper towels. Mix turkey, onion, garlic, ginger, egg, panko and salt in a bowl. Shape into 1 1/2-inch balls.
Warm vegetable oil in a skillet over medium-high heat. Cook meatballs, turning, until browned, about 8 minutes. Drain on lined plate; transfer to slow cooker. Scatter bell pepper on top.
Whisk together vinegar, soy sauce, sugar, crushed red pepper and 1 Tbsp. cornstarch; pour over meatballs. Cover; cook on low for 5 to 7 hours. Whisk remaining cornstarch into juice. During last 30 minutes of cooking, stir in pineapple and juice mixture.