CREATE TABLE table_30401 ("#  ( season # ) " TEXT, "No.  ( episode # ) " TEXT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Prod. code" TEXT)

Who wrote the episode with production code 2acx12?
SELECT "Written by" FROM table_30401 WHERE "Prod. code" = '2ACX12'
SELECT "Written by" FROM "table_30401" WHERE "Prod. code" = '2ACX12'