Am I the only one noticing a pattern with filler arc themes? Many of them have heavy reference to the main story. Here are a few examples:
Fuma Arc:
Sasume would do almost anything to be with her cousin, similar to Sakura with Sasuke.
Land of Birds Arc:
Lady Toki only valued her life for avenging her brother's murder, similar to Sasuke to his clan.
That episode with that summoned living castle:
It was there because one guy wanted revenge.