Stir together the cream cheese, Cheddar cheese, mayonnaise, ranch dressing mix, and garlic powder in a mixing bowl until evenly blended. Spoon some of the cheese mixture into each jalapeno half, wrap with half a bacon strip, and secure with a toothpick. Arrange the wrapped jalapeno halves onto a broiler pan.
Bake in the preheated oven until the bacon is no longer pink and beginning to brown, about 20 minutes.
