Who keeps saying those things

A man walked in to a bar after a long day at work. As he began to drink his beer, he heard a voice say seductively "You've got great hair!" The man looked around but couldn't see where the voice was coming from, so he went back to his beer.

A minute later, he heard the same soft voice say "You're a handsome man!" The man looked around, but still couldn't see where the voice was coming from.

When he went back to his beer, the voice said again "What a stud you are!" The man was so baffled by this that he asked the bartender what was going on.

The bartender said "Oh, it's the nuts--they're complimentary."