The original Flash Gordon serials

https://www.youtube.com/watch?v=ZTrSncxwGBE

I'm not suggesting that you need to watch the whole 3 + hours but it is interesting to me because when I was in grade school in Tucson we would go downtown on many Saturdays and watch westerns. The Flash Gordon serials were always shown before the main movie. They were 14-15 years old by then. They were my first introduction to movie S-F or almost any S-F because I didn't discover 'real' S-F until Jr. High.

In those days I was still traumatized by my first  movie experience (Bambi) as a three year old so any movies with 'scary' aspects were fraught with trauma. Flash Gordon was okay in that respect until they got to the episode with the Mole Men. That was a little jarring but I got through it. We never did see the end of the serials. I doubt if I'll watch it here....

The racial aspects of having Ming the Merciless being Asian is interesting because at the time, 1936, the Japanese had invaded China and atrocities were happening leading to Asians in general being morally suspect without naming the Japanese specifically. The Spanish Civil War was going on at the same time but since the opposing sides were both Caucasian it wasn't possible to 'choose sides' other than Communist vs. Nazis but those distinctions were beyond the interest of the average citizen at the time, other than the 'Lincoln Brigade".

https://en.wikipedia.org/wiki/Lincoln_Battalion