CREATE TABLE table_19501664_1 (original_air_date VARCHAR, us_viewers__millions_ VARCHAR)

Name the original air date for 15.74 viewers
SELECT original_air_date FROM table_19501664_1 WHERE us_viewers__millions_ = "15.74"
SELECT "original_air_date" FROM "table_19501664_1" WHERE "15.74" = "us_viewers__millions_"