Kenji Ohba, who would later make a name for himself playing two later Sentai heroes (Battle Kenya and Denzi Blue) and Space Sheriff Gavan, was one of the stuntmen who wore the Aka Ranger suit from Episode 63 and onward. He also appears out-of-costume in a few episodes (such as Episode 75) as an EAGLE soldier.
The actor for the Black Cross Fuhrer was changed from Mitsuo Ando (best known for his role as Professor Gill from Kikaider) to Nobuo Yana from Episode 54 and onward. Incidentally, Nobuo Yana guest-starred in Episode 53 as Dr. Shinigami (not the one from Kamen Rider).
General Magman was originally voiced by Eisuke Yoda for his first three episodes (42-44), before he was replaced by Shozo Iizuka (also the voice of General Temjin and Grand General Golden Mask).
Prop Recycling: Many of the Masked Monsters wore similar body suits such as Yakyū Kamen (Baseball Mask) and Terebi Kamen (TV Mask). The most notable is Tiger Kamen (Tiger Mask), who is a recycled version of Kōtetsutora Kamen (Steel Tiger Mask).