Preheat oven to 400 degrees. Line a large rimmed baking pan with parchment paper
Use a knife to pierce holes down both sides of the squash. Microwave the squash for 5 minutes. Carefully remove squash, it will be hot.
Cut squash in half lengthwise. Use a spoon to scoop out the seeds.
Drizzle both halves with oil and sprinkle evenly with salt and pepper. Place cut side down on the pan and roast in oven for 35-45 minutes, until tender. Use a fork to shred squash leaving it in skin.
Melt butter in a medium size skillet over medium heat. Add garlic and shrimp. Cook until shrimp is pink, about 4-5 minutes. Turn heat down to low. Stir in cream and cheese. Cook for 5 more minutes, stirring frequently. Remove from heat. Turn on oven to Broil.
Evenly top squash halves with alfredo shrimp mixture. Garnish with extra parmesan cheese and crushed red pepper flakes. Broil in oven for 2-4 minutes, just long enough to melt the cheese and brown the edges.