That was the original  never kick a woman before Turner colorized it in version later. No grwoth but you can see the term catfight as Olive turns into a cat after the spinach. She does grow muscles in her firght with the hillbillyy girl in the 1956 cartoon.

This was pretty cutting edge for 1936. They girl was suposed to appear again as a menace to Olive but censors killed it. Those bastards.

On topic, My first was I think the saved by the bell episode where the tall girl Jessie has a dreem about growing taller and taller. Granted it was cheesy and fake looking but it inspired me to imagine what it really would look like.

I really think it was the Incredible Hulk TV series.  When I was very young it would scare the crap out of me when Bruce Banner became the Hulk.  I'd run and hide.  I think over the years my mind must've become fixated on this and then upon adolescence asked itself, "Hey, what if that was a woman wearing the shirt that was tearing open, or a woman's foot violently ripping out of her boots?"

Also, seeing the Attack of the 50 ft. Woman remake growth scene really put the nail in the coffin, I think.

I have no idea.  I was stuffing my sister's Barbie clothes with cotton balls to simulate muscles as early as age 8 or 9.