Preheat the oven to 450 degrees F. Line a large rimmed baking sheet with aluminum foil and coat the foil with nonstick cooking spray.
In a large bowl, lightly whisk the eggs. Add remaining meatball ingredients and stir well to combine then use your hands to work the mixture until everything is well incorporated. Shape the mixture into meatballs about 1 1/2" in diameter and place them on the prepared baking sheet. Wet your hands, if needed, to make it easier to roll the sticky mixture. You should end up with 26 to 28 meatballs. Spray the tops of the meatballs lightly with non-stick cooking spray.
Bake the meatballs for 15 to 18 minutes, until lightly browned. They don’t need to be completely cooked through at this point.
Meanwhile, drain and reserve the juice from the can of pineapple chunks and set both the pineapple and the reserved juice aside.
In a medium mixing bowl combine the ketchup, all but 2 tablespoons of the reserved pineapple juice (reserve 2 tablespoons for later), soy sauce, brown sugar, mirin, rice vinegar, ginger root, and garlic. Whisk to combine well.
Spray the insert of a 6 quart slow cooker with non-stick cooking spray. Transfer the browned meatballs and the Sweet and Sour Sauce to the prepared slow cooker, stirring to coat the meatballs with sauce. Scatter the bell peppers and pineapple chunks over the top without stirring. Cover and cook on low for 2 hours. Remove the cover and stir to combine well, mixing the peppers and pineapple into the sauce. Combine the 2 tablespoons reserved pineapple juice with cornstarch in a small bowl and pour the slurry into the slow cooker and stir to combine. Cover and continue to cook for an additional 20 to 30 minutes until peppers are fork tender and the sauce is thickened.
Garnish with the green onions and sesame seeds and serve over rice for dinner or transfer to a bowl and serve with toothpicks as a party appetizer.