One of the kids in my computer class found out about netmsg and some of us started sending messages to each other. One day I saw a kid fell asleep at his desk, so I messaged him "wake up". It must have spooked him because when he woke up he called the teacher over and they puzzled over it together for a minute. I thought for sure since the name of the computer was in the message box and printed on a label on the computer that they would find out it was me, but nope lol
Another time in the same class I figured out how to create a local account so I could change the theme (it was Windows XP) to one I liked more. The teacher saw it when she was walking by and thought something was wrong with the monitor.
Other side of the building from the backdoor receiver.