"My daughter's birthday is near Halloween, which made planning her party easy. I adapted this recipe from one my mother used to make to fit the occasion. I made it expecting the kids would find it interesting but not likely eat it, so the adult guests could indulge. Boy, was I wrong! Can be made the day before."
In a large salad bowl, stir together the mayonnaise, horseradish, dry mustard, lemon juice, seasoned salt, and salt. Mix until the dressing is smooth.
Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once the water is boiling, stir in the rigatoni and return to a boil. Cook the pasta uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 13 minutes. Drain well in a colander set in the sink; rinse with cold water until the pasta is cool.
Place the rigatoni (guts), cherry tomatoes (monster eyeballs), black olives (eyes of newt), and water chestnuts (blind bat eyeballs) into the dressing, and toss to coat; stir in cauliflower (elven trees), zucchini (lizard bones), green bell peppers (magic grass), mushrooms (fairy stools), and shrimp (baby fingers) into the salad and toss again.