I remember at the time seeing the "Masked Rider Warriors" and just wondering "Where the hell did this lot come from. It wasn't until many years later I found out about Kamen Rider and those guys all being the predecessors of the main guy I'd been watching all series.
I remmeber the Power Rangers multi-parter, and found it weird that the Rangers were never acknowledged in Masked Rider and vice versa.
Come to think of it, was Dex ever seen during "Countdown to Destruction"? There were other Ranger allies like Trey of Triforia, the Aquitar Rangers, and Blue Senturion, yet the Masked Rider was nowhere. Dex Stewart is a dick.