Filler writers are like, "We'll make this EVEN BETTER than the real story! We'll have another character who is like Naruto! Except, he'll be like Sasuke too. He'll even have the Nine Tails Fox in him!"
Producer asks, "Wait... what? How can he have that?"
Filler Writers say, "Why not? We'll just say they collected that fart gas or whatever? Who cares? Won't it be be awesome to have another Nine Tails character?!"
Producer asks, "But.. what happens when the filler ends?"
Filler writers say, "Who cares."