In large bowl, combine meat, rice, egg and ½ of sauce, celery seed, salt, pepper, garlic and onion. Shape into small balls. Heat remaining sauce and water in cooker, using brown function or not closing lid. Drop meatballs in soup mixture.
Close cover securely, then bring up to high pressure and cook for 10 minutes. Let pressure drop of its own accord (natural pressure release). Serve over hot cooked noodles, rice or mashed potatoes.
If you don’t own a pressure cooker, you can cook porcupine meatballs on the stovetop. Heat a large skillet over medium-high heat and add the meatballs. Cook meatballs, turning occasionally, brown evenly. Drain and remove the grease. Pour the tomato sauce, 1 cup water, and Worcestershire sauce into the skillet; reduce heat to medium-low. Cover and simmer until the meatballs are no longer pink in the center and the rice is tender, about 45 minutes. Adding more water if the sauce becomes too thick.