Extensions 
 
            AppleShare's File Sharing "Holy Hand Grenade"
The development name for AppleShare was Holy Hand Grenade.  Thus we have the FileSharing Extension's creator 'hhgg'.  This is also from Monty Python.  By the way, the Apple Share PDS's "Killer Rabbit" was killed by the Holy Hand Grenade.  It is possible that it could also stand for "Hitchhikers Guide to the Glaxy", a popular book by Douglas Adams.
 
           Balloon Help
          Use Balloon Help on the icons of QuickTime and MacsBug.  You will see interesting information regarding the exension and document.

 
           Clippings Extension: Drag and Drop Game System 7.5
           If you type in “secret about box” in Stickies, or any program that has drag and drop capabilities, and drag it to the desktop you will get a secret game with credits. (system 7.5 only not 7.5.1, Clippings extension required)

Apple Headquarters              System 7.5.2 "Marconi"
On a Power Mac 9500 and 7500,  or any computer that has System 7.5.2, if you type "secret about box" no capitals in a text application, most likely Stickies, that supports the Clippings Extension, and drag the text to the desktop, you get a picture of the Apple headquarters and a flag in the foreground, with the logo "iguana iguana powersurgius".

By moving the mouse around you control the direction the flag is waving.  In fact, you can make it break off, fluttering toward the ground and off the screen.  The best way to get the flag to come off is to "whip" it back and forth (by moving the mouse up and down, at the right of the screen) and at just the right level of violence it breaks off.  Really cool, but sometimes it takes a while to reproduce.  Once the flag is off, you can control the direction of drift with the mouse.

There are rumors that there is more.  The warning in the text which scrolls by to "Watch out for low-flying iguanas" might be a hint.

Thanks to Ronald Bruck (bruck@mtha.usc.edu) for this egg.

 
            QuickTime "Project Warhol"
            The development name for QuickTime was Project Warhol thus an early version, known as the `warhol' init, had the icon of a Campbell's soup can.  It was not in QuckTime 1.0 so it is probably  a prerelease.

Also, in MoviePlayer go to "About QuickTime..." and watch the credits scroll by.  There is some interesting stuff slipped in.