Yep, that's Power Rangers in a nutshell. What got me back into seeing it firsthand was this review by MarzGurl:
http://www.thatguywiththeglasses.com/videolinks/marzgurl/reviews/11041-mightymorphin
I actually went back and watched some season 2 Power Rangers last night because something had been bugging me. I always knew that Jason, Trini, and Zack had been replaced with Rocky, Aisha, and Adam because they had demanded more money and were fired over it, but, as an adult, I began to think about that and realize that, if they had been fired, how did they pass their powers on to the new rangers. I remembered that episode! Jason, Zack, and Trini were there! I remember them being accepted to the Peace Summit in Switzerland and actively passing their powers on to the new rangers. It was very emotional. But how did that make sense?
So I went to YouTube and found the episodes and... holy shit! They were never there at all! It was all body doubles and stock footage, and it was very obvious! They hardly said anything. When they passed their powers on, they were completely in uniform, so you couldn't see their faces. Even after they'd passed on their powers, they were still in uniform when it made no sense for them to be. And before they had the chance to say anything, Zordon just went, "Jason, Zack, Trini. Goodbye, good luck... get out," and then just teleported them away.
But then I thought about it some more. I remembered that Rocky, Aisha, and Adam had been introduced before that, and the Peace Summit had been mentioned in earlier episodes as well. If both those circumstances only existed because Austin, Walter, and Thuy had been shown the door, how were they in those episodes?
Again... they weren't. When the six had to be shown together, stock footage, body doubles, and silence. But, for the most part, they didn't even bother. Tommy, Billy, and Kimberly would be hanging out, meet up with Rocky, Aisha, and Adam. They'd fight some putties. The trio would morph and continue fighting. Then, about halfway through the episode, Zordon would say, "Alpha, contact the other rangers." Then there would be a stock shot of Jason answering his communicator: "I read you, Zordon. We're on our way!" Then they were in costume, and they'd fight. The episode would end with, you guessed it, Tommy, Billy, and Kimberly meeting up with Rocky, Aisha, and Adam. "Gee, guys, thanks for your help. The other rangers would thank you too, but, they're, um, scuba diving or something."
And they managed to get away with this crap for... EIGHT EPISODES! And I never noticed! Sure, you say, you were just a kid. But I remember watching Back to the Future Part II several years earlier and immediately figuring out that all you saw of George McFly in 1955 were stock images from the first movie and the back of his head, and I knew that he had been replaced by a different actor. So how the hell did I never notice that half of the Power Rangers simply didn't exist for eight whole episodes?! It's mind-boggling to me!