I learned this prank from Liam Bastick – Excel MVP (Sumproduct company)…. Hope no one does it to me 🙂
By far and away the most popular ‘trick’ (in all senses of the word!) I demonstrate in training sessions is this monster.
Data Validation is a useful way to control what end users can type into a worksheet cell. You can use this functionality to play a trick. Please use this at your own risk: if you get fired, you will get no sympathy here.
If someone is unfortunate enough to leave a spreadsheet unprotected, simply highlight the whole worksheet and then activate Data Validation (Data -> Data Validation -> Data Validation… or ALT+D+L). In the ‘Settings’ tab, select settings similar to the following (the aim is to pick a number the user won’t be able to guess):
Then, select the ‘Error Alert’ tab:
Now, de-select the range and wait for your victim to use the worksheet. As soon as they type an invalid entry, they will be greeted with the following error alert:
“A fatal error has been detected on the hard drive. The hard drive will now be reformatted. All Existing data will be lost. Press any key to continue.”