Poke potatoes with the tines of a fork, and place them in the microwave oven. The more holes, the better. Cook on high power for about 4 minutes per potato. Check about halfway through, and turn potatoes over for even cooking. Potatoes are done when they can be easily poked with a fork.
Remove potatoes from the microwave, and cut each one in half lengthwise. Use a large spoon to scoop out the inside of the potatoes, leaving the skins intact. Place the scoopings into a large microwave safe bowl, and stir in the 4 green onions, sour cream, processed cheese, and 1/4 cup Cheddar cheese. Season with garlic powder, seasoned salt, and black pepper; mix well.
Place the bowl in the microwave, and cook for 2 to 3 minutes, or until heated through. Scoop the mixture back into the potato skins to serve, or serve from the bowl. Garnish with additional green onion and shredded cheese if desired.