Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How many millions of US viewers watched the episode titled "Happy Howl-o-ween"?

### Inputs:
table_name: table, columns: ['No in. series', 'No in. season', 'Title', 'Original air date', 'Production Code', 'U.S. viewers (millions)']

### Response:
SELECT U.S. viewers (millions) FROM table WHERE Title = "Happy Howl-O-Ween"