Fry bacon in a skillet until brown and crisp; transfer to paper towels to drain. Transfer grease to a measuring cup; if less than 1/4 cup, add plain oil to make 1/4 cup total.
When bacon is cool, chop into small pieces and toss with maple syrup. Set aside.
In a large saucepan, place bacon grease (with oil, if using) and popcorn kernels. Sprinkle with sugar and 1 tsp salt. Cover with a tight-fitting lid and place over medium heat until you hear a few kernels pop.
Once popping begins, hold pot and lid together tightly and shake pot every 1-2 minutes then return to heat (this will prevent the sugar from burning).
Once popping is done, carefully remove the lid, add remaining salt and stir with a large spoon. Add bacon-maple mixture and toss well before serving.