Cast the Expert: Of a sort. Riku (the original Kuuga) is played by Kenji Tominaga, Kuuga's suit actor.
Fake Nationality: Jean's actor, Serge Vasilov, is actually from Romania, while his character is meant to be French.
In Memoriam: Before the Heisei Rider era began with Kuuga's premiere, a message states that "This project is dedicated to Ishinomori-sensei". Shotaro Ishinomori was the creator of the Kamen Rider series, and Kuuga was an idea he had to revive before his death.
Old Shame: Averted.Thanks to a mistranslated interview, it was claimed for years that Joe Odagiri resented his time on Kuuga and took it off his resumé after moving on. He actually said that he didn't want to be typecast into children's shows, and there's evidence that he's at least neutral to the role: he kept in touch with his co-stars, attended Wakana Aoi (Minori Godai)'s wedding, and was committed to doing The Movie up to its cancellation. He has, though, said he doesn't really care for tokusatsu as a genre and took the role as a favor to producer Shigenori Takatera; since Takatera was fired due to the Troubled Production of Kamen Rider Hibiki, he has no real motivation to reprise his role.
A theatrical sequel to the TV series languished in Development Hell because the writers couldn't come up with a satisfactory conclusion to the story. Production was canceled in 2006, leaving Kuuga the only Heisei Rider series without a theatrical movie.
The early designs for Ultimate Kuuga had a much more regal (and gold) aesthetic. These would end up influencing the design of Rising Ultimate Form in Decade.
Masaya Matsukaze auditioned for the title role, but was ultimately passed over for Joe Odagiri. Considering he's been in multiple Super Sentai series, it's easy to imagine that Matsukaze would have been far more willing to reprise his role in later productions than Odagiri.