CREATE TABLE table_20163 ("No. in series" CLOB, "No. in season" CLOB, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "Original air date" CLOB, "U.S. viewers  ( million ) " CLOB)

Name who wrote the episode when the viewers was 1.81
SELECT "Written by" FROM table_20163 WHERE "U.S. viewers (million)" = '1.81'
SELECT "Written by" FROM "table_20163" WHERE "U.S. viewers (million)" = '1.81'