Many kids that had the Sega Master System found themselves feeling like 1980's hackers when they discovered the snail maze game that was snuck into the BIOS.
I was playing around with BIOS emulation today, fixing a flaw with the Korean BIOS when I had a play around with the good old SMS1 BIOS. To get the secret snail maze game you push UP and hold buttons 1+2 when you power on.
The strange thing is I know nearly all these mazes even though I have barely played them over the last 20+ years. I don't even need to look at the maze as a whole, I just know the direction to turn. It's funny how your memory can work like that for seemingly unimportant things.