Practical Jokes
Ethereal has many configuration options, and it can be configured to behave in completely unexpected ways. Assuming you can get access to someone's workstation when they're not looking, the following methods can cause quite a bit of confusion.
Disappearing Packets
Select View->Coloring Rules from the menu and create the following rule:
Name: (doesn't matter)
Filter string: frame
Foreground color: white
Background color: white
Make sure the filter is at the very top of the list. You'll end up with a display that looks like this:
The packets disappear because the display filter "frame" matches every packet. Setting the foreground and background to the same color (whether it's white, black, purple, or pink) makes the packet list unreadable.
Disappearing Protocols
Select Analyze->Enabled Protocols from the menu, click Disable All, and save. Ethereal will display everything it knows about each packet, but it won't be much:
