Question: What episode number in the series was viewed by 13.66 million people in the U.S.?
SQL: SELECT MAX("No. in series") FROM "1-25668962-1" WHERE "U.S. viewers (million)" = '13.66';

Question: How many million U.S. viewers watched the epiode with a production code of 1ARC12?
SQL: SELECT "U.S. viewers (million)" FROM "1-25668962-1" WHERE "Production code" = '1ARC12';

Question: How many million U.S. viewers watched the episode with a production code of 1ARC03?
SQL: SELECT "U.S. viewers (million)" FROM "1-25668962-1" WHERE "Production code" = '1ARC03';

Question: How many million U.S. viewers watched episode number 6 in the series?
SQL: SELECT "U.S. viewers (million)" FROM "1-25668962-1" WHERE "No. in series" = 6.0;

Question: Who directed episode number 18 in the series?
SQL: SELECT "Directed by" FROM "1-25668962-1" WHERE "No. in series" = 18.0;