Actually, filler episodes can be very useful. If they use the episodes to give more depth on certain characters. They can cause viewers to see "different sides" of the character. They can instill more emotions, for example, I recall a dragonball z episode when vegeta & goku were fighting. (my memory is kinda fuzzy) but vegeta was explaining how he was raised after the destruction of the saiyen's planet. He went off into details, which were very interesting. (I'm not going to explain them, just in case someone doesn't know) My point being, when the episode was over, I knew a lot more about his past, which I was able to relate to his present thus understanding why he acted like he did in that present episode (to a point). So filler episodes open a very large door of opportunity, it's just up to the developers wether or not they utilize it.
