Many many variations exist -- JeffManteiMurphy's Law is about human error, not about outrageous fate.
Murphy was a real guy. According to legend, the prototype of Murphy's Law was used in his performance review: "If there is a wrong way to do something, Murphy will find it." Actually, according to the JargonFile, Murphy was not the one who made the mistake that inspired his law (a technician methodically connected 16 electrodes to a test subject backwards in a rocket-sled test), but rather the guy responsible for finding out what went wrong. His original formulation was apparently "If there are two or more ways to do something, and one of those ways results in catastrophe, then someone will do it that way."
The guy in the sled, who took all that punishment for nothing, was Col. John Stapp (http://www.ejectionsite.com/stapp.htm). He's pretty famous among aerospace engineers. You can also thank him for seat belts and crash-testing of automobiles. If you've seen the stock black and white film clip of the guy in the sled with his face all pushed around, that's him. The connectors weren't keyed, so it's not clear whether we should blame the technician or the guy who designed the harness.Don't know where I got first encountered it, but above my desk (yes, at work too!) I always have something that reads "When you look to see how the system works you usually find that it doesn't." But that's not why I came by ... I came to leave a link the collection of variants (Murphy's Laws on Science and Technology) -- BenTremblay
Related regulations, policies, rules and observations:
a GumptionTrap: to forget to install the small vital part (e.g. piston ring) inside the large complex part (engine), and to realise after you've washed the oil off your hands. You will need to take it all apart and start again.