The Between the Lines blog recently had a post on AutoCAD Pranks. This post will cover a Civil 3D 2009 prank. The first thing you need to do is down load this VBA file. To run the file type VBALOAD at the command line and select the file. Next type VBARUN and select a subassembly object. Once you select the subassembly object it will go from something that looks like this:
to something that looks like this:
The change won't affect how the corridor is built. To get the subassembly back to the original look, go the Properties of the Subassembly, the Parameters tab and press OK. Civil 3D 2009 should then rebuild the subassembly based on the dll file.
For a more disastrous prank take a look at this post. Instead of importing points, add data to the surface that is large difference from the highest or lowest point on the surface while the surface style doesn't show contours. Then save and close the drawing. Once an unsuspecting person opens the file and sets the surface to show contours it will either crash the program or take a really long time to draw the contours. Since I did the original post Civil 3D 2009 does a much better job of handling the task and will take a larger elevation difference to cause the program to crash.
I personally wouldn't do any of this, but there seems to be some people out there who like to mess with others.