One of the age old questions of the Pokemon fandom is what someone believes to be filler and non-filler. So what do you personally think is a filler episode and what isn't a filler?
For me, anything that doesn't happen importantly plot-wise like a gym battle or a solid character development episode can be considered a filler. Usually these types of episodes have a COTD formula and a problem that is presented and solvable within the episode.
As a general reminder, this thread is merely to discuss what you feel is a filler and what isn't a filler.
Whether or not you think filler is important to the flow of the series should go in this thread, and the individual series' that you feel has the most entertaining filler should go in this thread.