In another song, he merely walks in stylish designer outfits. By taking care of these trivial details, the makers have earned some respect from the audience.
The Narcolepsy angle has been used very effectively from the story's perspective. We are told that only water (in the shower or rain) keeps our hero from falling asleep and when we see how water becomes a very important aspect of the story, you smile in amazement. Of course, we don't know if water does really keep Narcolepsy patients from falling asleep, but we just have to accept that because in the film it does help the hero. It's debatable but I wouldn't argue because it makes sense the way it has been used in the film.
