In the early 80s when videos were in their infancy, the company I worked for had a promotional video made.
The Midlands region staff were all invited to a showing of the video in the board room and as I was the only office-based employee that had any idea how to set up and operate a video player. I was given the task.
I swapped the promotional video for a porno that I'd rented from a video shop in town that lunchtime and got it ready at a particularly raunchy part of the movie.
The regional manager gave the video a great build-up but didn't see the funny side once I'd pressed 'Play', unlike the others in the room.
I got summoned to his office at 7.30am next morning to be given a dressing-down but thankfully his sense of humour had returned even though he tried to hide it