- Ass Pull: Dr. Noroi is the true Big Bad. A character introduced in the final moments of the final episode with no foreshadowing, who's stated to be the manipulator behind it all, and to have been a key enemy to Keisuke's father, inspite of never have being mentioned.
- Awesome Music: Totsugeki Kamen Rider X plays during the Apollo Geist vs. X fight.
- Ensemble Dark Horse: Apollo Geist was this, to the point that they chose to bring him Back from the Dead in lieu of creating a new character. He later became the Dragon-in-Chief in Kamen Rider Decade.
- Memetic Mutation: Starfish Hitler is more well-known in the toku fandom than everything else from the show combined. Even non-Rider fans are familiar with it.
- Narm: Starfish Hitler has to be seen to be believed.
- Squick/Nightmare Fuel: In the manga, a female friend of Jin's gets squished by a boulder thrown by a GOD kaijin in EXTREMELY gory fashion.
- They Wasted a Perfectly Good Character: After his father is killed, he uploads his brain onto a computer, and becomes a new base for Keisuke. By episode 2, the computer realizes he's holding Keisuke back too much and blows himself up, never to be mentioned again.
- They Wasted a Perfectly Good Plot: The series actually started out with a fairly compelling mystery surrounding Keisuke, his father, Ryoko and Kiriko. It's all rushed and concluded by episode 8, with Ryoko's betrayal and subsequent reveal as The Mole having no bearing on the remainder of the series. The three are barely mentioned afterwards.
- What an Idiot!: Apollo Geist kills one of the two scientists who resurrects him for failing to stop Rider X, and much later realizes that he needs both men to repair his body. While short sighted, it's understandable because Geist hadn't known that the procedure would end with his body degrading and that he'd need both of them. Upon learning that he needs the Perfecter (to replace his heart) to save himself... Geist kills the other professor, even though he'd probably need that man to install the Perfecter. All the money, time and effort it took to bring in two of Japan's greatest minds, and the tech to bring Geist back was clearly well spent.
YMMV / Kamen Rider X