Who needs colleagues?
I did once flip the reset switch on a client's machine. I had been planning to do so later on, to give them some practice in running the equivalent of fsck, but not quite then. This was during the installation and training phase, not production, so nothing was lost but time (ten minutes?) and face.
On the other hand, I was at a tech day when my phone informed me that certain of our servers were down. This proved to be so, and I hopped the Metro back to the office. It turned out that the SAN tech, while doing I know not what preventive maintenance, had flipped the power switches with his shoulder. Everything started up again nicely, to our and his relief.