Romi Park's previous role in the equally Jidai Geki-inspired Samurai 7 has her character forming an attachment to someone called Kyuuzo. Here, it's someone called Juuzo. For added points, 'kyu' and 'juu' translate into 'nine' and 'ten'.
Ryuunosuke's worst fear is, oddly, cacti. Ironically, one of Aiba's previous roles cast him as Fuji Shuusuke in The Prince of Tennis musicals, a character who loves cacti and owns quite a number of them.
Enforced Method Acting: Takeru's actor, Tori Matsuzaka, has stated that he was the only one of the main cast told beforehand that Takeru is a Body Double for Kaoru in order to achieve realistic reactions from the others when The Reveal was filmed.
Fake Nationality: While Richard Brown was implied to be American, his actor, John Kaminari, is actually Italian and can speak Japanese fairly well. His strange accent was meant to make him sound like a strange foreigner. As well, the fact he's humble, earnest, perfectly willing and eager to adapt to another country's customs and ideals, and obsessed with learning the path of the samurai means he can't easily be slotted as one of the two Eaglelander base types; he's 100% Ascended Fanboy who just happens to be from elsewhere.
Hey, Shinken Blue! Your serve!note Hiroki Aiba was Shusuke Fuji in the musicals and the Movie Which makes the Kamen Rider Decade crossover even more fun...note Masahiro Inoue played Keigo Atobe in one of the musicals
Masaya Matsukaze (MegaBlue) makes an appearance in episode 45 as the real former ShinkenRed, Kaoru's father.
You may recognize Rin Takanashi from the 2007 film adaptation of the Japanese novel Goth as one of the lead characters, Yoru Morino.
If It Swims, It Flies: Kame, Kajiki and Ika Origami (sea turtle, swordfish and squid, respectively) are direct examples.
Implacable Man: Pulled off spectacularly in the Closing Act: The Shinkengers approach Dokoku in SamuraiHaOh, which is reduced to TenkuShinkenOh and then just ShinkenOh from his barrage. And they don't flinch once.
Dokoku was this a few episodes prior. To distract him while Kaoru draws the sealing character, all the samurai attack en masse with every upgrade at their disposal. He doesn't even blink when they hit him, and then sends them all flying with a single attack.
Name's the Same: Takeru shares his name with another character who's - Surprise! - also a Super Sentai Red Ranger, Red Mask.
Averted in America, where Power Rangers RPM, based on Shinkenger's predecessor Engine Sentai Go-onger, was supposed to be the last series - until Saban bought the PR franchise back from Disney and began work on adapting Shinkenger.