My personal sign is when you start seeing awkward collaborations start cropping up. One time when I was thrifting, I picked up a graphic novel that had the Justice League, team with the Power Rangers of all things. I glimpsed into what the plot was about out of morbid curiosity and it was just a plain generic time and dimension thing.
Nothing ever connected between the teams at all. DC Comics, while fledgling at times with how they go about their series and movies, still have far more relevance than Power Rangers do. I think the Power Rangers are just grasping at straws to keep being relevant when people have largely moved on from them.
It’s an episode almost or entirely composed of clips from previous episodes. Usually it has some sort of a framing device - for instance, in an adventure show, it might be the characters taking a ‘breather’ after a tough encounter and musing on how they got here. Or one character might confront another about a situation that’s been brewing, and the clip show is showing bits of that situation leading up to the confrontation.
On an aside, reception to clip shows is an interesting shift. For a long time, one or two were an accepted part of a long-running series - either because it let you make an episode on the cheap using recycled footage, or because in the pre-internet-streaming-on-demand world, it let audiences catch up on what had been happening in episodes they might have missed or seen months ago.
Nowadays, however, they’re almost universally viewed negatively, as their reason for existing is absent and they’re mostly taken as a sign of poor planning by the creators.