I don't know how anybody can think the boxing episode of NuBSG was a filler. I don't remember a ton, but from what I do remember that was a huge episode that filled in a ton of the questions about what happened during the recent time jump . The boxing matches were also a way for some of the characters to resolve conflicts that had been building up during the episodes before it. It was probably one of the most important episodes of that season.
It might not have moved the overall plot of the show forward much, but it was a massive character based episode.
It might not have moved the overall plot of the show forward much, but it was a massive character based episode.