Preheat oven to 400 degrees f. Slice the zucchinis in half lengthwise. Use a spoon to scoop out the insides of the each of them. Cut off the stems, then cut the hollowed out zucchinis in half.
Place the zucchinis onto a baking pan, then brush the tops with the olive oil. Mix the parmesan cheese with the garlic powder then sprinkle it evenly over the oiled zucchinis. Bake for 12 - 14 minutes or until the tops are golden brown.
While the Zucchini is baking, fry up the bacon until it's crispy. Chop up the cooked bacon and grate the cheddar cheese. Cover the tops of the zucchinis with the grated cheese and chopped up bacon. Place back in the oven and bake for another 4 -5 minutes or until the cheese is melted. Remove from the oven and sprinkle with the chopped green onion. Place a small dollop of sour cream onto each of the zucchini skins. Serve hot.