It's dark under my desk. I can't see well, and I know that the hole is there somewhere. I for some reason had unplugged my headphones, and now I wanted them plugged back in. I just crammed the plug into the first hole it came to and my whole computer went black. Oops.
I wish I had had the headphones on so I could have heard if it made a noise or not.
I quickly pulled it back out and saw I had inadvertantly plugged into a USB slot. Whoops. After a moment or two the computer came back on and started up. It gave me a "windows shut down abnormally" (or whatever) error, and then when it came up it reconfigured my network configuration (what?). After that everything was back to normal.
So... now you know what happens if you try and stick your headphones into a usb jack. Go forth and prosper!