This episode serves two purposes
1) to avoid the "Previously on Avatar" becoming longer than the actual episode when the finale aired by having it recapitulate every major event of the show (which it did quite well) and 2) to create an honestly hilarious parody of the very show which aired it. And it was quite funny.
Is it a filler episode? Yes but I don't care. It's funny. Does it really make sense for the playwright to know that much about the characters journey? No but that's in the same category as "why didn't Aang freeze to death when he was in the South Pole/North Pole when he's not dressed for that weather?" it's something that doesn't truly make sense but which we accept for the premise.
Story and character-wise. Toph and Zuko have a nice heart to heart about Uncle Iroh and it works on Katara and Aang's relationship but that's not the part of the episode I most care about. I'm here for the humour and this episode more than delivers in that regard. Ten on ten.
Is it a filler episode? Yes but I don't care. It's funny. Does it really make sense for the playwright to know that much about the characters journey? No but that's in the same category as "why didn't Aang freeze to death when he was in the South Pole/North Pole when he's not dressed for that weather?" it's something that doesn't truly make sense but which we accept for the premise.
Story and character-wise. Toph and Zuko have a nice heart to heart about Uncle Iroh and it works on Katara and Aang's relationship but that's not the part of the episode I most care about. I'm here for the humour and this episode more than delivers in that regard. Ten on ten.