CREATE TABLE table_4077 ("No." FLOAT, "#" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. air date" TEXT, "Production code" TEXT, "U.S. viewers  ( million ) " TEXT)

Who wrote the episode with 3.96 million US viewers?
SELECT "Written by" FROM table_4077 WHERE "U.S. viewers (million)" = '3.96'
SELECT "Written by" FROM "table_4077" WHERE "U.S. viewers (million)" = '3.96'