Preheat an outdoor grill for medium heat, and lightly oil the grate.
Mix together the cream cheese, Parmesan cheese, garlic powder, and Cheddar cheese in a bowl until the mixture is thoroughly blended.
Lay a jalapeno pepper onto a work surface, and cut a lengthwise sliver from the side of the pepper, exposing the seeds and white membrane. With the handle of a teaspoon, scrape out the seeds and membrane, leaving the hollow pepper. Repeat for the rest of the peppers. Chop up the pepper slices, and mix into the cheese stuffing. Stuff each pepper with cheese mixture, and wrap each stuffed pepper in a half bacon slice. Secure with toothpicks.
Grill the poppers on a less-hot part of the grill until the peppers are hot and juicy and the bacon is browned, 30 to 40 minutes.