Abandon Shipping: Jasmine used to be the most shippable Dekaranger, that is until every pairing with her got abandoned in the 10 Years After upon confirming that she's now married with Hikaru, of all people.
Author's Saving Throw: The judgement on the Alienizers. In the series, the judgement is done in about 10 seconds by the "Highest Court in the Universe." That seems awfully quick to make a literal life or death decision (although some aliens who got judged did not get death sentences). Come the 10 Years After movie, it turns out that the court is on a planet that is time-displaced eight months for every 10 seconds of Earth's regular time, giving each criminal a more substantial trial.
Complete Monster: Agent Abrella sold many weapons supporting galaxy-destroying wars for fun and profit to most of the Alienizers, regardless of how many lives were taken. Once a galaxy is destroyed, he moves to the next to generate profit and destruction. Abrella treats any and all crime as a business opportunity, and it doesn't matter if you're destroying cities, selling slaves, pawning stolen merchandise, or filming child pornography, as long as the price is right, he'll be more than happy to sell you the tools you need to further your enterprise. And his Villainous Breakdown near the end of the series was caused merely because the Dekarangers were ruining his transactions. Yes, Abrella himself caused a citywide destruction spree and nearly destroyed the whole of the Space Police just so he could keep his job.
Harsher in Hindsight: If you've seen Tensou Sentai Goseiger, watching the scene in Full Blast where Deka Gold is only able to transform for a second before being on the receiving end of an attack by the villains is a lot harder to watch, considering that something very similar happened to Gosei Green, who's played by the same actor as Deka Green,, except he died as a result.
Hilarious in Hindsight: Originally, the planned name for this series was "Sirenger". However, this was changed due to the fact that there was an Eroge by the name of Sirenger, and Toei wasn't able to get the copyright. The full name of the eroge, ironically enough, is Tokumei Sentai Sirenger.