[sircastor]

I don't remember how I learned it, but back when my family had a IIci I remember there was a startup key command you could press to display an image of the developers in the ROM. I kind of miss the days when that sort of thing was done.

[spogbiper]

similar on my childhood radio shack computer - https://www.cocopedia.com/wiki/index.php/CoCo3_Easter_Egg

[ASalazarMX]

As a kid I didn't have Internet yet, but somehow had a CoCo3. Many times I pressed Ctrl+Alt+Reset and wondered what was the purpose of this image, I even made a BASIC program to dump it on tape from the ROM. Didn't learn the answer to that mystery for many years.

[wkjagt]

Computers were still something special back then. I miss that too.

[wslh]

In the Commodore Amiga you can turn off and on the power light. Weird for these times.

[kevindamm]

On the Sega Master System there was an entire game in the ROM -- Snail Maze (the walls and floor reminiscent of the company's logo). Pressing up-left and both buttons while turning on the console with no cartridge in the slot would start the game.

[kalleboo]

On the Macintosh Classic, there's a whole OS boot disk image in ROM that can be activated by booting with the keys "command option X O" held down (X-O was the code name for the machine). These are the remains of a prototype for making a diskless terminal Macintosh. It comes in handy if you've hosed your boot disk somehow.

[unwind]

That is because the power indicator LED also serves as an indicator of the audio low-pass filter. Rather quirky, yes.