CREATE TABLE table_24869 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT)

Name who wrote the episode that aired april 9, 1989
SELECT "Written by" FROM table_24869 WHERE "Original air date" = 'April 9, 1989'
SELECT "Written by" FROM "table_24869" WHERE "Original air date" = 'April 9, 1989'