>>53428306Self contained episodes or arcs in a show based on a serialized manga, book, etc. that has run out of manga or book material to adapt. The Pokemon anime has always been its own original narrative, it doesn't need to come up with its own material to let the primary source run ahead more. It is its own primary source, based on another property but with its own unique continuity.
Dummies have taken filler to mean any episode that doesn't directly advance (my idea of what) the "plot" (should be), and that was and still is wrong especially in this case. MPM is precisely the story the writers and staff wanted to tell. It's just not what a bunch of very butthurt people wanted from them. That is the damned opposite of "filler"