"Go Go Kamen Rider"
"Go Go Kamen Rider" was simply episode 13 of the series shown on a movie screen. It featured Tokageron and 10 revived previously killed Shocker monsters.
When Taki breaks into what he believes may be a Shocker base he finds himself in a room full of "statues" of Shocker monsters. The owner of the place claims to be a collector and demands that Taki leaves, so he does. After Taki has left the "statues" come to life.
The "collector" is of course Tokageron. Kamen Rider loses his first battle with Tokageron.and has to train to gain a new combat move.
Being simpley epsisode 13 this "movie" of course features Kamen Rider #1. Taki, Kazuya (Chiba, Jiro) is actually the main character because Fujioka, Hiroshi who played Hongo, Takeshi already had the motorcycle accident which removed him from the series until his leg healed.