So apparently the firmware for a number of of the old PPC Macs had Easter Eggs embedded within them and, with the right combination of woo, you could get the firmware to spit these Easter Eggs out for you to view.
‘Downtown Doug Brown’ has a lovely narrative on how he figured out how to extract one such Easter Egg – a development team image embedded in the ROM of a 27 year old Power Mac G3.
The entire story can be read here.