user: Question: When was originally aired the episode with an audience of 1.57 million us viewers?
Columns: ['Series no.', 'Season no.', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: [32.0, 1.0, '"The Boy with the Pancakes Tattoo"', 'Lake Bell', 'Ken Marino & Erica Oyama', 'August 10, 2012', 411.0, '1.64']
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "U.S. viewers (millions)" = '1.57';