System 7.0 

With ResEdit, take a look at STR# resource -16415 in the System file.

The first string in the resource reads "May you code in interesting times." (Posted to Usenet by Nigel Stanger)

Also, while running System 7, try renaming a disk to "Like Wow Man. HFS For 7.0!" (where the space after 'Man.' is actually an option-space; you'll have to type this somewhere else like the Notepad then cut/paste it into the disk name).  Then eject the disk with Command-E, and double- click on the greyed-out disk icon.

The Mac will ask you to please re-insert "HFS for 7.0 by dns and ksct". (The intials are of David N. Feldman and Kenny S. C. Tung, who wrote the HFS extensions for System 7.)  Other disk names work, due to the way the name is checked; try "KMEG JJ KS" or "Hello world JS N A DTP". 

(Found by Francois Grieu and mentioned in TidBITS #143)