Well, not exactly. But still very fun. My friends and I found that, on my school's mac network, we can forcefully "screen share" with another person while they're using it. No administrator password/account required, just the use of an account called "student" that is installed on every computer at the school.
Steps to reproduce (try it without admin accounts):
Open Finder.
Go to the Network.
Find the other computer, and open it (make sure screen sharing is enabled).
Click on screen sharing in the upper right corner.
Login as a non-admin account on that computer.
Go nuts!
Edit: More fun things to try: log on to a computer remotely and talk to people
.
Side note: screen sharing from computer A to computer B while B is already looking at A's screen results in one of those infinite mirror effects. Also, it won't crash your computer over short periods of time, so feel free to test it.
Steps to reproduce (try it without admin accounts):
Open Finder.
Go to the Network.
Find the other computer, and open it (make sure screen sharing is enabled).
Click on screen sharing in the upper right corner.
Login as a non-admin account on that computer.
Go nuts!
Edit: More fun things to try: log on to a computer remotely and talk to people
Side note: screen sharing from computer A to computer B while B is already looking at A's screen results in one of those infinite mirror effects. Also, it won't crash your computer over short periods of time, so feel free to test it.