Does this exist? (I might have made it up, but I don't know)

The premise is as follows: A very skilled cheerleader (or gymnast?) has her mind mostly taken over by a stereotypical male action hero (covert or special ops). In times of danger, the cheerleader/gymnast's skills are used in rather frightening ways to subdue (or kill?) attackers.

I'm not sure if I've completely made this up. I know Buffy was a cheerleader and I feel there's some suggestion here to Last Action Hero wherein Jack Slater's daughter pretended at being a damsel in distress before utterly brutalizing her attacker.

If this premise has played exactly as I've described, I don't know who plays the cheerleader/gymnast and who plays the "action hero". I'm pretty sure if it happened, it was live-action and not a cartoon, but it also feels like it was more than a while ago and not a recent idea. I also am not clear whether it was on television. This may have been only one episode.

All that I know for certain is that I can't find any suggestion to it online purely by Googling.

Wait, has Batman ever swapped bodies with a cheerleader?

I can't recall anything with exactly the plot you've described, but I wouldn't ne surprised if they exist. The action hero in ordinary people circumstances was practically a subgenre of it's own in the 90s. Probably still is but I remember a ton of comedies coming up with that kind of premise in the 90s. The body swapping/taking over bit isn't as prevalent, but there's still enough movies like that for me to easily believe it exists.

Probably not what you're looking for, but this relates in terms of regular students/cheerleaders acting out of character in violent ways:

1998's Disturbing Behavior is an "invasion of the body snatchers" type of story set in a high school. A group of outcasts notices that one by one their classmates, even follow geeks and outsiders, show up one day as jocks and cheerleaders with a side effect of violent tendencies.

Quote:

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They find out that mind control is being used to make unruly teens become perfect so they can function properly in life, but the programming has some glitches that lead to momentary relapses and violent fits.

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

Depending on how long ago you saw this movie, your brain may be an unreliable narrator of the events that happen. This is at least adjacent to what you're talking about and you might enjoy it, anyway.

Maybe Ninja III: The Domination?

A friend of mine was just saying he watched this hilariously awful movie from the 80’s and sent me a trailer for it. Almost looks like it is similar at least.