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Serena Williams doesn't have time for silly questions.

The No. 1 tennis player, who's vying to finish off the calendar grand slam in the U.S. Open, sat for a press conference after her quarterfinals win against her sister Venus Williams. One reporter thought it'd be a good idea to ask her why she wasn't smiling and laughing more after her victory, and he quickly found out that was a bad idea.

While that was a pretty irrelevant question to begin with, the fact that Williams also was exhausted made for a bad mix for that reporter.

Luckily, he now knows not to mess with Williams when she's tired. Or ever, really.

Thumbnail photo via Robert Deutsch/USA TODAY Sports Images