* ''Series/KamenRiderDenO'' is a series about time travel. In an alternate timeline where she never met her astronomy-loving boyfriend, the main character's sister gives her cafe a flower theme, instead of an astral one. [[spoiler:A character from the future is revealed to be her daughter. Her name? Hana, which means flower.]]
* Towards the end of ''Ore, Tanjou!'', the [=DenLiner=] makes a sidetrip to the time when Ryotaro was born, allowing Ryotaro and his younger self to see his parents for the first time. Hana is also seen looking out the window as well... [[spoiler:because it's ''her'' first time seeing her grandparents.]]
* Den-O's form when possessed by Sieg is the Wing Form, meaning he uses wings to attack. Sieg is a swan-themed Imagin. Swan wings can break human bone.
* At the end of the series, [[spoiler: when Ryotaro believes the 5 Heroic Imagin he fought alongside have vanished]], he calls the names of all of them...except for Sieg. At first I thought this was just because the writers had forgotten about Sieg in that exact moment, but then I realized why: [[spoiler: Sieg has spent the shortest amount of time with Ryotaro - the number of episodes he appears in can be counted on one hand; unlike the 4 Taros, he has not made that many memories with Ryotaro, so it makes sense that Ryotaro wouldn't miss him that much]].
* Some of the enemy Imagin are based on riders from [[Series/KamenRiderRyuki Ryuki]] - the Bat Imagin is based on Knight, the Crust Imagin is based on Scissors, and so on. However, the titular rider from that series doesn't have a corresponding enemy Imagin. This might seem odd...until you remember Ryutaros's dragon motif - if he hadn't decided to change sides because of his feelings for Airi, he would be an enemy Imagin, and if he hadn't named himself, he would be the Dragon Imagin!