Granny's Chicken Tetrazzini

1 chicken, cooked and deboned
8 oz cooked spaghetti
1 can cream of celery
1 can cream of mushroom
1 small jar pimientos
1 large jar cheez whiz (start with slightly less)
1/2 bell pepper, sauteed
1 onion, sauteed
1 cup milk

Combine all ingredients together and bake in casserole dish for 30-45 minutes.