MMPR's Friend in Need Arc
One can say that Toei did have the idea of Kamen Rider and Super Sentai crossovers but it was done only on stage. Power Rangers isn't purely copy/paste depending on who the producer is and here, Saban tried to promote his failed Mashed Rider with the three part special "Friend in Need". So my thoughts? So I did HATE Saban's Mashed Rider due to poor quality but I thought that, Sentai SHOULD try to do this the first time I saw it.
The concept was this- Masked Rider was crammed into the Power Rangers' universe to which the Power Rangers must fight to defend Edenoi. I thought the idea was cool but it was basically flopped by poor writing. But still the idea was cool. Here Lord Zedd considers Count Dregon an "old rival" though it was never explored in Saban's Mashed Rider. The fight scenes were pretty lame but still, the idea was cool.
The story was where Dregon enslaves Edenoi (scenes taken from Black RX involving Crisis Empire, and FYU Dregon's counterpart General Jack was just a subordinate to Grand Lord Crisis) and the planet was once lush was later desolate. It's sort of like that episode in Black RX when Kotaro ends up in the world of the Crisis Empire, discovering that the world was slowly dying. The Power Rangers enter minus Kimberly (because she was sick) to which Lord Zedd and Rita take advantage by sending a monster.
Despite having three parts, I felt the whole arc lacked some quality. For one, I thought that Kimberly's peril was a bad plot. Two, the whole fight scenes were heavily relying on stock footage. After they were called back to Earth, Dregon decides to attack Earth next... which however neither Dregon nor Zedd mentioned each other again.
But the legacy managed to create Toei's crossovers namely the Shinkenger Arc in Decade, Super Hero Taisen (which is EVEN worse), Super Hero Taisen Z and ToQger vs. Gaim.