I was in a public place on my laptop, and my laptop went into hibernation to save battery. I switched it back on and then the laptops BIOS came up saying that the battery was critically low, nothing bad here.

Instead of clicking continue, I decided to press "Diagnostics" instead. The diagnostics immediately began to run in the BIOS.

The screen began to show different coloured bars and patterns, obviously a screen test. Then a prompt appeared asking me if coloured bars were displayed. The options were yes and no, and a button saying "Exit" in the top right. Me, not wanting to do a full diagnostics on such a low battery, pressed exit.

The screen turned black, and then flashed red. The beeper on the motherboard began to beep at an ear-piercing volume. It sounded as if it was a bomb about to go off. Everyone around me stared and some people began to even panic. I tried switching it off by holding the power button but nothing was happening. People were just staring all around me.

After about 10 seconds, the beeping stopped and the screen displayed an error message similar to this:
"CRITICAL ERROR: Monitor test FAILED.
No user input was provided."

Moral of the story: Make your program account for all possible options.