Preheat the oven to 400°F. Lightly spray a non-stick baking sheet with oil. In a large bowl, combine the ground chicken, panko crumbs, egg, scallions, celery, carrot and garlic; season with salt and pepper, to taste. Using clean hands, mix until combined. Roll the mixture (1/8 cup each) into 26 round meatballs. Place meatballs onto prepared baking sheet and bake until cooked through and golden, about 16 to 18 minutes. Place the meatballs in a bowl, add the buffalo sauce and gently toss to combine. Serve immediately, drizzled with blue cheese dressing, if desired.