CREATE TABLE table_2226817_4 (written_by VARCHAR, original_air_date VARCHAR)

Name who wrote the episode that aired april 9, 1989
SELECT written_by FROM table_2226817_4 WHERE original_air_date = "April 9, 1989"
SELECT "written_by" FROM "table_2226817_4" WHERE "April 9, 1989" = "original_air_date"