Cash Cow Franchise: Den-O has been living on well beyond the year-long expectancy of its fellow Rider series, and doesn't look to be dying anytime soon. Lampshaded in the opening Imagin skit in Farewell, Den-O.
"Well, for all the talk of 'Last' and 'Farewell', it's always common practice to make a sequel, isn't it?"
The Cast Showoff: Takeru Satoh portrays 1 character who's gained a total of 7 different possessed personalities (some of them by force), sings in every version of Double-Action (except Gaoh Form, Coffee Form, Climax Form, and Strike Form), his own solo song, Real-Action, and, thanks to Ryutaros, has an excuse to demonstrate his breakdancing skills.
Fan Nickname: Thanks to the Egyptian-looking collar and other elements, Shiro is sometimes called Kamen Rider Phara-Oh.
Because of his skull and crossbones mask and resemblance to Gaoh, he's also sometimes known as Gaoh Pirate Form.
Irony: The premise of the Cho Den-O trilogy: the films shine the spotlight on Zeronos, New Den-O and Diend, shoving Den-O himself in a supporting role instead. (Fans did complain about Den-O becoming a Cash Cow Franchise, after all...)
Prop Recycling: The movie Riders use reworked Den-O suits; taking it a step further, Gaoh's suit was used to create Yuki, which is the reason Diend Complete Form doesn't have a Den-O representativenote The producers wanted to use Gaoh, but couldn't because they didn't have the suit anymore, so they decided to just leave Den-O unrepresented, although one does have to wonder why they didn't just use Nega Den-O instead, considering that they used Ryuga instead of Verde to represent Ryuki
A few of the Imagin were reworked from others; for example, the Owl Imagin from Ryutaros' character focus episodes was turned into the Bluebird Imagin that appears late in the series. More obvious examples include the Leo and Albinoleo Imagin (both of whom are Kai's subordinates) and their Leo Soldiers (reworked from ZECTroopers).
Romance on the Set: Takeru Sato (Ryotaro) and Rina Akiyama (Naomi) dated for a while in 2008.
Star-Making Role: Of all the Kamen Rider main actors, Takeru Satoh is the actor with the most abundant post-Rider career.