Narcolepsy is actually a relatively 'common' disorder occurring in 1 in 2000 people. The National Institute on Neurological Diseases and Stroke reports that Narcolepsy usually starts during the mid teen years to 25 years old. The term narcolepsy was created by the French physician Jean-Baptiste-Édouard Gélineau. It was formed out of two Greek words 'narke' meaning "numbness" or "stupor" and 'lepsis' meaning "attack" or "seizure"
A seizure causing numbness is probably the best description of narcolepsy as it presents in a similar way to Epilepsy. The brain short-circuits (likely due to a genetic and viral interplay) and causes the sufferer to have daytime naps that come out of no where as well as sudden paralysis known as cataplexy.
When scientists study the brain waves of narcoleptics, they find that they have abnormal sleep-wake cycles and rapid onset Rapid Eye Movement (REM) sleep. REM sleep is characterised by a deep sleep state where you are motionless and floppy, and like the name suggests, there are fast movements of the eyes. A healthy sleeper will only enter the REM phase after at least an hour of sleep, however, narcoleptics can experience REM sleep after as little as 5 minutes! This is not as advantageous as you may think.
To be able to fall into a deep sleep quickly is great when it is voluntary, but not when it comes on as an 'attack' almost daily. The first symptom to appear is Excessive Daytime Sleepiness (EDS) which is simply feeling (and looking!) sleepy most of the day despite getting a good night's sleep. EDS can destroy your work life and cause major issues in close relationships - falling asleep on the job or during an argument does not bode well long-term. The worst is that the attack is often precipitated by a strong emotional trigger - a good laugh, a strong rage, excitement.... falling asleep and missing out on life's big moments can't be fun.
I imagine a new mom passing out as handed her newborn baby; a student sleeping in his chair as he is about to graduate; or a nervous employee dozing off during their performance review. I don't think that narcoleptics get the same sympathy as epileptics as their 'sleep seizures' don't look quite as abnormal but are probably equally as dangerous. I imagine narcoleptics are in harm's way during many ordinary daytime activities like bathing/showering, driving a car, cooking and/or doing water sports.
The good news is that once diagnosed using the Epworth Sleepiness Scale, narcolepsy can be well managed (but not cured). If concerned, take the test and get the help you need.