Cook the bacon in a large, heavy skillet over medium heat until crisp, about 8 minutes. Transfer the bacon with a slotted spoon to a paper-towel-lined plate.
Add the oil to the fat in the skillet and increase the heat to medium-high. Stir in the garlic and cook until very fragrant and golden, about 1 minute. Stir in the collards, 3/4 teaspoon salt and 1/2 teaspoon pepper and cook, turning with tongs, until the collards are tender and bright green, 3 to 4 minutes.
Meanwhile, cook the spaghetti in a large pot of boiling salted water until al dente. Reserve 1 1/2 cups of the pasta cooking water, and then drain the pasta.
Toss the spaghetti with the collards and some of the reserved pasta cooking water. Toss in the cheese and season with salt and pepper. Crumble the reserved bacon over the spaghetti and serve sprinkled with the red pepper flakes.
From Food Network Kitchens