Invasion of the Body Snatchers?

For every "Forbidden Planet" there were dozens of things like "Taboo World" and such. And the elements that resonated with audiences would go on to become tropes in other sci-fi movies.

Local TV networks used to show all the knockoffs late at night on Fridays & Saturdays. The movies were cheap (sometimes free) to license and provided a lot of opportunities to sell ad time to local businesses. It was very lucrative at the time.

This is basically how the original fanbase for "Mystery Science Theater 3000" was created. Kids who grew up watching all these cheap, cheesy sci-fi flicks loved watching them all over again with Joel & the bots.

Of course, nothing of this ecosystem has survived into the Internet age.