This isn't really a hint as much as it is an amusing OS X glitch that I've never seen documented. I don't know how long this has been present, as I just discovered it recently.
If you use the speech service (whether through the Services menu, the say Terminal command, or an application) to speak the word bullfrog, OS X says bullfrogs. If you instead have the system speak bullfrogs, it says bullfrog.
What an odd little thing.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090301194827510