1. Whisk together 1 can of the condensed cream of shrimp soup and the 3 cups milk in a large saucepan until well blended. Bring to boiling over medium heat. Remove saucepan from the heat. Stir in shrimp and rice. Cover; let stand for 5 minutes.
2. Transfer the shrimp-soup mixture to large bowl. Stir in imitation crabmeat, sweet red pepper, slightly thawed peas, the remaining can of shrimp soup, the Old Bay seasoning, salt, black pepper and half-and-half. Transfer mixture to a lightly oiled 13 x 9 x 2-inch baking dish, spreading the mixture evenly. If serving next day, refrigerate, covered, overnight.
3. Heat oven to 375 degrees F.
4. Bake casserole, covered, in 375 degree F oven for 55 minutes. Uncover baking dish; scatter crumbled crackers evenly over the top of the casserole. Bake for another 15 minutes or until the top is golden brown. Let the casserole stand for 10 minutes before serving. Makes 12 servings.