Preheat the oven to 375°F. Cook the pasta in salted boiling water until 2 minutes shy of al dente.
In a large bowl, combine chicken, cream cheese, ranch dressing, hot sauce, and bleu cheese.
Toss the pasta in the mixture, transfer to a baking dish then sprinkle cheddar cheese over the pasta. Bake for 20 minutes. Garnish with scallions and serve immediately. Happy nomming!