Rinse scallops thoroughly in cold water; drain well. Combine scallops, cracker crumbs, 1/4 cup butter, catsup, sugar, salt, and pepper; stir well. Spoon scallop mixture into a greased 1 1/2- quart casserole or 6 greased 10- ounce custard cups.
Combine green onion and remaining butter; sprinkle evenly over scallop mixture. Bake at 350° for 30 minutes or until lightly browned. Serve immediately.