Incidentally, Arisa Komiya joining the cast means that we have three previous Yellow Rangers that are regular or recurring cast members, joining MaoIchimichi and Hiroya Matsumoto, who himself was also her former teammate as Masato Jin/Beet Buster.
In Space 39, Stinger sang the song of Oushiza no Uta, which is actually a twist of the original song, Sasoriza no Uta
Acting for Two: Taiki Yamazaki plays both genders of Naga's people, although while playing a female he is dubbed over by voice actress Ayumi Tsunematsu.
Fake Shemp: Space 25 deliberately brings back a slew of past characters as solidified memories from the Kyurangers, but Professor Anton gets this treatment but averted later on with the character returning for real.
Scorpio Kick: Scorpio's finisher move, as it looks similar to a Rider Kick (especially Kiva's Rider Kick). Bonus points for having his actor being a former Rider himself.
Uchu Sentai Kyuranger: Civil War: The post-series V-Cinema special Uchu Sentai Kyuranger vs. Space Squad, which has the Kyurangers divided into two sides over whether or not to believe in Hammie after her supposedly going rogue.
Recycled Set: It's your usual Toei tokusatsu shooting areas, but with filter and props to make it more alien. In particular is the Planet Jonjon's bar in Episode 1 which was the cafe from Kamen Rider OOO.
The Cast Showoff: On more than few occasions Yosuke Kishi (Stinger) has shown off a very nice singing voice.
Up to Eleven: Sixteen years ago, Gaoranger set a new precedent for mecha combinations with a total 20 seen on-screen; this season's nine-man base-set team and Scramble City combination style allows for the Kyurenoh to have a possible 1,680 combinations, before even properly introducing a Sixth Ranger!
Early scans indicated that Ohguma Skyblue was intended to be a full-fledged suit with the Koguma decals removed, instead of the Attack of the 50-Foot Whatever powerup for Koguma Skyblue.
There's no Kyuranger vs Zyuohger. This is possibly due to the series itself taking place in an Alternate Universe than the rest of the Super Sentai series, but it is speculated that the real life reasons are actor unavailability and a general decline in success and interest for the Vs. Movies as a whole. The closest to said team up is the Kyurangers making an Early-Bird Cameo in Zyuohger vs Ninninger and the two teams being among the teams who took part in the battle in Kamen Rider × Super Sentai: Chou Super Hero Taisen.
Interestingly, it's worth noting that if one does hack the Seiza Blaster, there is a sound effect for a Zyuohger Kyutama, suggesting that either the crossover was planned at one point, but scrapped, or they weren't sure if they would go ahead, and ultimately decided not to.
If one hacks the Seiza Blaster toy, a Gemn Kyutama sound effect can be creatednote if one uses the regular Ex-Aid Kyutama on the Dark Seiza Blaster, it will register it as the Gemn Kyutama, suggesting that it's possible that the crossover with Kamen Rider Ex-Aid was going to be a full-blown TV special as opposed to split between episodes of each shownote presumably, the Gemn Kyutama would've been used to summon Dan Kuroto, since assuming the crossover occurred after episode 7 of Kyuranger/episode 24 of Ex-Aid, Kuroto would've been dead.
Although Kyuranger could still be adapted into a Power Rangers season, it's extremely likely that had Saban renewed their toy manufacturing partnership with Bandai of America (as opposed to partnering with Hasbro), it would've been adapted instead of Tokumei Sentai Go-Busters after Ninja Steel finished, as it was stated that the cube gimmick from Zyuohger was not feasible for merchandise, and it was unlikely that they'd skip straight to Lupinranger vs Patranger.
Kyuranger vs. Space Squad has a humorous credits scene that specifically points this out, with Luka showing up and getting into an argument with Raptor, while Hammie looks on and remarks that they seem kinda similar for some reason she can't quite place.
The Seiza Blaster is voiced by none other than Gian himself.