Preheat oven to 400°F (200°C). Line a rimmed baking sheet with aluminum foil. Line a plate with paper towel.
In a medium skillet over medium-high heat, cook the bacon, stirring often, until brown and crispy, about 5 minutes. Transfer the cooked bacon to the prepared plate; set aside.
In a medium bowl, add the cream cheese, cheddar cheese, garlic powder, and pepper and mix to combine; set aside.
Starting at the bottom of each jalapeño, carefully slice each pepper in half lengthwise, cutting through the stem. Use the tip of a small spoon to remove and discard the seeds and membranes from each pepper.
Fill each jalapeño halfway with the cheese mixture, about 2 to 3 teaspoons depending on pepper size. Lay the stuffed peppers cut side up on the prepared baking sheet.
Bake until the cheese is melted and bubbly, about 10 minutes.
Top the peppers with the crumbled bacon and the sliced green onion. Serve.