The hunt begins
Since the early days of computers, playful programmers have been hiding messages in their code. Much like carving one's initials on a tree stump or a bathroom stall, these messages typically have one purpose: to say "I was here."
In the Atari 2600 era, these hidden digital messages came to be known as "Easter eggs" by Atari engineers after programmer Warren Robinett hid his initials in the seminal 1979 video game Adventure. Presumably, the Easter egg analogy originated because these messages are like hidden "eggs" (or treats, if you will) which must actively be found.
Macintosh SE (1/2)
Many Apple products have secrets buried in their ROM chips (read-only storage devices that typically hold low-level software). The 1987 Macintosh SE is no exception, containing not one but four hidden photographs of the Mac SE development team.
Macintosh SE (2/2)
Here's another one of the four hidden photos.
To see the photos on a real Macintosh SE, press the interrupt switch on the left side of the machine (if your Mac is equipped with one; it's one half of a pair of developer buttons that snaps into place) to get into the Mac debugger program. Once in the debugger, type "G 41D89A." The images will display in a never-ending slideshow. To leave the slideshow, hit the other developer button (reset).
Macintosh IIci / IIfx
The popular Apple IIci also contains a secret photo of its development team hidden in ROM. To see the image, set your monitor to 8-bit color and set the system date to September 20th, 1989 (the IIci's release date). Then restart the machine while holding down Command-Option-C-I. A color photo of the IIci development team will appear on the center of your screen with the inscription "Copyright Apple Computer, Inc. 1981-1989."
Interestingly, a similar procedure will work on the Mac IIfx. This time, set the system date to March 19th, 1990 (the release date of the IIfx) and restart while holding down Command-Option-F-X. You'll see the same developer team photo as the one displayed on the IIci.
Generally, if you're lacking a system boot disk for a Mac, you're out of luck. You can't use the machine. But if you own a Macintosh Classic, you might be surprised to know that it contains a fully functional copy of System 6.0.3 hidden away in its system ROM.
To access it, turn on the machine and hold down Command-Option-X-O. You'll soon be presented with the classic Mac desktop from which you can make a copy of the OS on disk, run AppleShare, or simply use it as a bare-bones OS installation.
Apple Fax Modem
Another audio Easter egg shipped in the very rare 1988 Apple Fax Modem (which is so rare that the author could only locate one fuzzy black and white photo of it). Owners of that modem could hear a digital recording of the modem's three developers speaking their names (Peter, Alan, Neal) if they followed this formula:
While holding down the front panel button, switch on the modem. It will beep three times. After the beeps, press the button three times with the same timing/rhythm as the beeps. If you get the timing right, you'll hear the names. (Afterwards, send me a photo of your modem, because they're very hard to find.)
So far we've seen two photo-based Easter eggs and one that packs an OS surprise. But Apple has hidden away a number of audio-based secrets in its products as well. One of the most famous came with the ROM Version 3 model of the Apple IIgs. To access it, power up the IIgs. When you see the Apple symbol moving back and forth, press Control-Open Apple-Option-N. You'll then hear a recording of the IIgs design term shouting "Apple II!" through the system's speaker.
For those of you without a IIgs to tinker with, you can find a WAV file recording of the Apple II shout on this site.
Macintosh Quadra 840AV (1/2)
We've seen photos of Apple computer developers in black and white and in color, but they've both been relatively boring seated group photos. One of the two images stored inside the Mac Quadra 840AV's ROM ups the excitement level by showing the 840AV development group relaxing on a beach with an inset photo of a dog.
Macintosh Quadra 840AV (2/2)
The other shows the group on some sort of bridge or elevated walkway...and there's that dog again.
These images require extraction from the ROM using more difficult techniques than simply holding down a key combination; the brave among you can try to find the images, which are actually encoded as JPEGs, with tools found on MacKiDo, an entertaining site which contains more information on Apple Easter Eggs.
Happy egg hunting!