Cook spaghetti according to package directions, reserving 1/3 cup pasta water; drain. Meanwhile, whisk together soy sauce, rice wine vinegar, peanut butter, ketchup and honey; set aside. In large sauté pan or wok, heat oil over high heat; cook celery, carrot, red pepper, onion and garlic, stirring, for 2 to 3 minutes or until vegetables are tender-crisp. Add soy sauce mixture; cook, stirring, for 1 minute. Add cooked pasta, reserved pasta water and chicken. Cook, tossing gently, for 2 to 3 minutes or until well coated and chicken is heated through. Garnish with peanuts and green onions.
Tip: For extra spice, garnish with sliced red chili peppers.