CREATE TABLE table_31186 ("No." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Featured character ( s ) " TEXT, "U.S. viewers  ( millions ) " TEXT, "Original air date" TEXT)

How many million U.S. viewers was written by Matt Pelfrey?
SELECT "U.S. viewers (millions)" FROM table_31186 WHERE "Written by" = 'Matt Pelfrey'
SELECT "U.S. viewers (millions)" FROM "table_31186" WHERE "Written by" = 'Matt Pelfrey'