For example: there's a specific kind of case-making Caddis larva that will use its mucus (or some kind of secretion) to form a kind of rope to tether itself to a rock on the stream bed. It can & will suspend itself by this tether while floating in the current. Well, as luck would have it, their tether will sometimes become dislodged from the rock, sending the larva tumbling down the stream where it becomes an easy meal for a trout.
Enter the ever-thinking angler.....some fly fishers will, armed with this knowledge, paint the first few inches of their tippet behind the fly white (while fishing an imitation of this cased larva) in order to copy the appearance of one of the above mentioned unfortunate larva.
Another example: I have known anglers who have kept their flies at home in the refrigerator, embedded in Limberger or other smelly cheese. As you may know, Limburger is a very smelly cheese. These folks claim that by making their flies take on the smell of the cheese it attracts the fish to their flies like nothing else.
Hmmm? Well personally, I'm not about to start painting my tippets or storing my flies in cheese, but who am I to argue with someone who's catching fish? I will sometimes rub my nymphs in the mud from the stream bed & I do believe that the color(s) of my fly are important. I have a few other practices I do which make sense to maybe only me - & that's the point. If it makes sense to you & you've has success doing it (& you're not breaking any laws), then go ahead & do it (in a humane way, please). Let everybody else laugh. Hey, they all laughed at Edison & Einstein, too so you're in good company! To the non-angling population we fly anglers all appear to be at least a little crazy at best. If we are, I'm fine with that. It's one illness I'm happy to have. Just keep those stinky flies away from me!!!