user: Question: How many millions of US viewers watched the episode titled "Happy Howl-O-Ween"?
Columns: ['No in. series', 'No in. season', 'Title', 'Original air date', 'Production Code', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'real', 'text']
Sample row: [21.0, 1.0, '"A Doomed Christmas"', 'December10,2011', 121.0, 'N/A']
SQL:

assistant: SELECT "U.S. viewers (millions)" FROM "Table" WHERE "Title" = '"Happy Howl-O-Ween"';