Start by cooking (soaking) the rice noodles. Boil enough water in a pot for the rice noodles to easily soak. Once the water comes to a boil, remove from heat.
Add the rice noodles and cover for 10-12 minutes. Drain before adding to the stir fry.
Next, prep the sauce. In a small bowl, combine the rice vinegar, fish sauce, soy sauce, ketchup, brown sugar and red pepper flakes. Stir until the sugar dissolves.
Thaw the shrimp. If needed, remove the tails and devein. Sometimes cooked shrimp will already have this step done.
Chop the bell pepper. Mince the garlic. If you are using canned bean sprouts, drain from the can liquid.
In a large skillet or wok, heat the sesame oil over medium-high heat. Stir fry the bell peppers for a couple minutes, they should blister.
Then add the shrimp, bean sprouts and garlic. Cook for another couple of minutes.
Push everything to one edge of the pan and turn the heat down slightly, to medium. Add the egg and stir to scramble, then stir the other ingredients into the egg.
Add the noodles and pour the pad thai sauce over everything. Stir fry so everything gets coated in the sauce and gets hot. I use tongs to toss everything easily.
To serve, top with chopped cilantro, green onions and peanuts. Squeeze a little fresh lime juice over everything.