ADD & narcolepsy share very similar external appearances (such as inability to concentrate on boring things....) & have been mistaken for eachother. Luckily their medication is also very similar - so it probably hasn't mattered all that much & maybe they are actually closely related?.

In narcolepsy the REM sleep surfaces unusually quickly at the onset of sleep - and can intrude into the waking state. This causes stunningly "real" auditory, visual & tactile hallucinations - which could be similar to those "movies" someone mentioned above & also rings bells with the multiple internal conversations thing. There is a theory also that some narcoleptics counteract their fatigue by artificially maintaining a high state of stimulation - both by switching their attention rapidly & by risk-taking.

Narcoleptics also tend to have high IQs - and the blessings of the condition include an amazingly rich dreamlife, unbelievably weird hypnagogic hallucinations, & (possibly consequently) a tendency toward the creative. There are downsides (& some narcos really have a very hard time - there's quite a variation in symptoms), but its good that some "disorders" have really positive sides too. Always look on the bright side of life.........