CREATE TABLE table_16467 ("No. in season" FLOAT, "No. in series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( million ) " TEXT)

Who wrote the episode that aired on April 17, 2011?
SELECT "Written by" FROM table_16467 WHERE "Original air date" = 'April 17, 2011'
SELECT "Written by" FROM "table_16467" WHERE "Original air date" = 'April 17, 2011'