CREATE TABLE table_25518 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT)

The episode which originally aired on December 17, 2004 was written by whom?
SELECT "Written by" FROM table_25518 WHERE "Original air date" = 'December 17, 2004'
SELECT "Written by" FROM "table_25518" WHERE "Original air date" = 'December 17, 2004'