Never attribute to Malice that which can be explained by stupidity
While this is a wonderful statement, the "malice" part is more fun:
Example 1: Most character terminals, being monochrome, had simple deflection systems. Some of the coils inside had a simple two position connector that with little effort can be installed the "incorrect" way given a little "push". Opening up a terminal and swapping said connector can be most fun to an unsuspecting victim/sucker/co-worker. It can take a few hours of all sorts of "how could that happen" and mad diagnosis attempting to find a solution.
Example 2: While working at Apple, a co-worker described an 'init' routine that decreased the screen size 1 pixel in each direction every time the machine re-booted. The effect of this "screen shrinker" are fascinating. In his developing work, he thought his eyes were going bad as the screen shrink day by day. It was just a little, but over time it became significant. The victim was finally told of the "hack" and let in on the prank. It was much fun while it lasted.
Example 3: (Not really IT related) Back when gas economy was not THAT important (read the '60s), someone had purchased a VW Beetle. He would come to work and brag about his mileage every time he filled up his tank. Then one of his co-workers would add a little gas (remember it was "cheap" then) to his tank, the bragging became worse. More was added over time, and the "zillions of miles per gallon" ensued. Then he stopped adding gas, and down it went., not getting so much now, and he would run out of gas every once in a while. It ended the "bragging rights" of the VW owner. I suspect that this was before VW's had gas gauges, so it was pre-1964 or so. For the UK: gas == petrol.
We now return you to your regular program. Yes, BOFH's existed even then!