CREATE TABLE table_28521 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "Production code" CLOB, "U.S. viewers  ( million ) " CLOB)

Which production code had original air dated february20,2011
SELECT "Production code" FROM table_28521 WHERE "Original air date" = 'February20,2011'
SELECT "Production code" FROM "table_28521" WHERE "Original air date" = 'February20,2011'