Want to show your geeklings some real retro computing? How about showing them the emacs easter eggs built into emacs. There is a MUD, the game of Life (the cellular version, not the board game version), ASCII Tetris, and a primitive AI for Psychoanalysis.
Easter eggs are fun, hidden features that are implemented in software for the user to find. The developers of emacs (the text editor built into Mac OS X, and many other Unix-based systems) included many hidden Easter eggs to be discovered by its users. We’ll highlight a few of them here for you to try out.
via Terminal 101: 4 emacs Easter eggs | Mac|Life.
I think that you mean ‘a’ text editor built in…..