My Web site has a page that describes how to access the Easter Eggs in Excel 95, 97, 2000, and 2002. Greg Schultz, at Tech Republic, takes it one step further and provides lots of screen captures: Looking back at Microsoft Excel Easter Eggs.
In the past, Microsoft’s developers used to go to great lengths when it came to secretly embedding Easter Eggs into their products. I stress the word past, because Microsoft now officially bans the practice for security reasons as part of their Trustworthy Computing initiative.
The increase in the prevalence of malware led to the notion that undocumented code embedded into a major application could be used to compromise sensitive or confidential data. In fact, many companies and government offices forbid the use of software containing Easter Eggs for security reasons.
Here’s an example: The Hall of Tortured Souls, featured in Excel 95.