Sekai Seifuku: Bouryaku no Zvezda - Shin Zvezda Daisakusen

Recommended only if you just want to see a little bit more of the characters from the main series.
It is a short, conventional story centered mainly around Roboko, who independently of Zvezda wants to audition for an idol group. Compared to the other episodes, this felt very lackluster and poorly paced. I don't dislike it because it's an idol story though, that could really well done - this just felt a little contrived, even compared to the rest of the show. What I do like is that it showed just a teensy bit of how things are with the cast after the end of the ... last episode: getting to see Asuta and Renge working together in their battle outfits, and a certain couple returning from a honeymoon made it worth the time, and that's about it.