Bring a pot of water to a boil. Add noodles, remove from heat, and let soak until noodles are softened, about 15 minutes. Drain.
Mix ketchup, sesame oil, fish sauce, soy sauce, and red pepper flakes together in a bowl. Set aside.
Heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Add shrimp; saute until firm and opaque, 3 to 5 minutes. Remove shrimp and add remaining oil to the skillet.
Pour eggs into the skillet; cook and stir until lightly scrambled, about 5 minutes. Add green onions, bean sprouts, and garlic. Cook until fragrant, about 1 minute. Add the noodles, ketchup mixture, and cooked shrimp. Cook for 3 minutes more. Sprinkle with peanuts.