[via Reddit] Apple Computers have had a special “Apple” key since the days of the Apple //e and //c, where the “open-apple” key (which had the outline of the Apple logo on it) was the equivalent of pressing the button on paddle 0, while the “closed-apple” key (which had a solid apple logo on it) was the equivalent of pressing the button on paddle 1.
When the Macintosh was being designed, they added the now-familiar “command” symbol to the Apple key, and the story of why is documented on Folklore.org. Here's a snippet:
We thought it was important for the user to be able to invoke every menu command directly from the keyboard, so we added a special key to the keyboard to invoke menu commands, just like our predecessor, Lisa. We called it the “Apple key”; when pressed in combination with another key, it selected the corresponding menu command. We displayed a little Apple logo on the right side of every menu item with a keyboard command, to associate the key with the command.
One day, late in the afternoon, Steve Jobs burst into the software fishbowl area in Bandley III, upset about something. This was not unusual. I think he had just seen MacDraw for the first time, which had longer menus than our other applications.
“There are too many Apples on the screen! It's ridiculous! We're taking the Apple logo in vain! We've got to stop doing that!”