Switching your computer's keyboard with the keyboard of the computer next to you is a classic computer lab prank. Usually, the person opens Notepad or a word processing program and types into it. However, I am going to show you how to take this prank to the next level with Command Prompt.

These instructions will only work if the computers in your lab run Windows, but they usually do. Some schools have a Mac lab, but a school that has one of these usually has at least one lab with Windows computers.

I am not responsible for anything that goes wrong as a result of this prank. Don't take things too far (don't cause an outbreak of virus/hacker hysteria), know when to stop (e.g. when the person looks like they're catching on to you), and as with all pranks, don't pull it on someone who won't find it funny or will try to beat you up if they find out you did it. This is especially important with this prank in particular, because there is a high risk of being "caught".

Step 1: Swap the Keyboard Plugs

Sit next to the person you want to pull the prank on. Wait for the person sitting next to you (your victim) to get up and leave their computer for a moment. You may have to create a distraction, perhaps by telling a friend who's in on it to ask them for help with something. Go behind your computer and the computer of the person you want to pull the prank on. Unplug your computer's keyboard and plug it into their computer. This won't work if your lab's computers use PS/2 plugs, but those are uncommon these days. Most computer lab computers use USB keyboards, which are hot-swappable (you can plug them in and unplug them without shutting down and restarting the computer).

There are two ways you can go from here. If you want to have a two-way conversation with the user, and they haven't locked the computer, then unplug their keyboard and plug it into your computer. After this, use your mouse to click on your Start menu. Go to Accessories->Notepad. Everything the other user types in will appear in this Notepad window.

If you don't want to do this, then leave their keyboard plugged in. They will still be able to use their computer normally, but you will be able to disrupt any typing they do, in addition to executing all of the following steps.

The rest of this Instructable - the fun part - is pretty much the same regardless of which of these two options you pick.

Step 2: Open Command Prompt

Press WIN-R on your keyboard. This will open the Run prompt on the other person's computer. You could then type in "notepad" and press Enter. This would open Notepad on their computer, and you can type whatever messages you want into it. That is how this prank is normally done.

However, we're not going to do that. We're going to be using Command Prompt. Why? Well, simply put, it looks like the windows that pop up during hacking scenes in movies and TV shows. Many people in this day and age probably never seen Command Prompt before. Technologically-illiterate users won't have a clue what's going on, and even some more tech-savvy users could be confused or startled.

Step 3: Talking to the User

Once Command Prompt is open, you can talk to the user through it. Type a line of text into Command Prompt and hit ENTER to start a new line. Once you've hit ENTER on a line, you can't go back and change it. It's kind of like texting. You can only move the "conversation" forward.

First, I recommend typing "echo off". This command tells Command Prompt not to display the directory (the "C:\Users\..." stuff) whenever you enter a command. That stuff could be distracting, so I recommend using "echo off".

From there, you can type in whatever you want to type! However, there is one VERY important thing to note. You must enter a colon(:) at the beginning of every line. If you don't, then Command Prompt will think you're trying to give it a command and will throw up an error message about the command not being recognized. Colons, however, cause the compiler to ignore text placed after them. These are used in batch files (automated scripting files) to add comments.

What will you say to the user? That's up to you. There are multiple scenarios you can play out. You can pretend to be the computer, a ghost haunting the computer, a hacker, a virus, or something else I haven't thought of. But whatever you do, REMEMBER TO PUT A COMMA AT THE BEGINNING OF EVERY LINE!

I highly recommend opening Command Prompt on your own computer to practice using it before trying this prank out. You can open it the same way I showed you earlier - by pressing WIN-R and typing "cmd" - or you can find it in your Start Menu under Accessories->System Tools (if you don't have Windows 8). If you have Windows 8, press the Windows key (WIN) and search for "command prompt".

Step 4: Changing Color!

Command Prompt allows you to change the text color and background color. Turning the text red and saying "ERROR: SYSTEM FAILURE" or "VIRUS DETECTED" can really scare some users. You do this by entering the command "color xy", with color x being the background color and color y being the text color. You have 16 colors available to you, numbered 0-F in hexadecimal. The image above shows what each one looks like, and the list below shows their names and numbers.

0 = Black
1 = Blue
2 = Green
3 = Aqua
4 = Red
5 = Purple
6 = Yellow
7 = White
8 = Gray
9 = Light Blue
A = Light Green
B = Light Aqua
C = Light Red
D = Light Purple
E = Light Yellow
F = Bright White

Changing the text color to green ("color 0A") will make it look like the cliche "hacking" text you see on TV and in movies. Historical note: the reason this cliche exists is because many of the PCs available thirty years ago, when computer hacking began in earnest, had monochromatic green displays. (The IBM 5150 is an excellent example of such a computer.) For some reason, that image of green text on a black background remained in our collective memory, long after those monochromatic monitors and command lines gave way to full-color displays and GUI systems.

You can really freak people out by using red text ("color 0C") - they'll automatically assume it's something bad, like a virus or a cyber-attack. In hacking scenes in movies and on TV, red text is used to show computer-illiterate viewers that whatever is on screen is bad - a virus, an illicit file, or something else nasty.

Of course, your victim may notice the "color" commands on the text, but they won't necessarily make the connection - and even if they do, they still won't know what's going on!

Step 5: What If They Click Away?

If the user clicks on something other than your Command Prompt window, it will deselect that window. Once the window is deselected, you won't be able to type into it. There's nothing more you can do, so prank over, right?

Not so fast.

All you have to do is press ALT-TAB. This will scroll through the programs that are currently open - including Command Prompt. Scroll until you're back on Command Prompt. If their computer is next to yours, you should be able to see what's going on. If it's not, you may have to guess. Once you've selected it, you'll be able to type in it again, and the prank can continue!

Step 6: Return Control to the User

When you've had your fun, or when you suspect the other user has started to catch on to you, let them have their computer back. Get out of the Command Prompt window by typing "exit" and hitting ENTER. This will exit the Command Prompt session.

If you plugged their keyboard into your computer, you will then have to plug it back into their computer. Either get them to leave their computer (again) or let them know the whole thing was a joke and explain what happened. Hopefully, they'll be relieved and think the whole thing was funny.

Whatever you do, don't forget to plug your keyboard back into your computer! Don't leave either computer set up to do this prank, because that will annoy the next person who wants to use it.