Melt butter in saucepan; add flour, cooking & stirring until light brown. Stir in paprika, salt, pepper & cayenne. Add onion, green pepper & garlic; cook over low heat 5 minutes, stirring. Remove from heat & add lemon juice, Worcestershire & oysters (which have been picked over & heated in own juice). Pour into greased 1 1/2 quart casserole; top with cracker crumbs. Bake in 400 oven for 30 minutes or until bubbly.