Here in south Louisiana fresh shrimp is only as far away as the neighborhood grocery stores. If you can't get fresh shrimp it's okay to use frozen just don't get the precooked shrimp or it will end up too rubbery from overcooking. Shrimp cooks so fast that when we do boils the shrimp only go in for 3-5 minutes depending on the size AFTER the fire has been turned off.
Cook the fettuccine as directed on the pkg. Drain and rinse well and set aside.
Saute the bell pepper, onions and celery in the butter until the onions start to look clear. Add the garlic and cook for another minute or two (not too long or it will burn).
Add the half and half, the cajun seasoning, and the velveeta cheese. Simmer until cheese is melted. If you want the sauce thinner, add a little more half and half . Remove from heat and add the shrimp, the parsley and the fettuccine.
Transfer to a buttered or sprayed casserole dish and sprinkle parmesan cheese ovr top. Bake uncovered at 350 F for 20-30 minutes, or until bubbly.