Cook the pasta in a large pot of salted boiling water until al dente, about 8-10 minutes. Drain and rinse under cold water.

For fresh shrimp, cook in a skillet for 2-3 minutes until pink. If pre-cooked, chop into pieces and cool.

Chop celery, red bell pepper, red onion, and parsley. Set aside in a mixing bowl.

In a bowl, whisk together mayonnaise, sour cream, Dijon mustard, lemon juice, and Old Bay seasoning. Adjust seasoning to taste.

Combine cooled pasta, shrimp, imitation crab, and chopped veggies in the large bowl. Pour the dressing over and toss gently.

Cover and chill in the refrigerator for at least 1 hour before serving.