That's only the tip of the iceberg.
The menu-driven version of apt (aptitude) has some Easter Eggs in it as well. The help for aptitude (displayed with the --help option) states that "This aptitude does not have Super Cow Powers." Also try:
(The '-v' option increases the verbosity level, to display more detail. More 'v's increase the verbosity level, e.g. '-vv'. Go ahead and keep trying it with increasing numbers of 'v's.)
And if you've got a newer version of Python installed (3.0 or later), launch the Python interactive interpreter and type:
There are lots more, those are just the ones that come to mind off the top of my head.Edit
: Just remembered a couple more:
If you're running the GNOME desktop, hit Alt-F2 and type:
If you have OpenOffice 3.1 or older, open the spreadsheet application and enter the following formula in any cell (I believe this one works on the Windows version as well):