I'm trying to remember the title, author, or year of posting of a "foals learn to curse" story which has basically the same comedy beats as this scene in "Flutter Brutter" (season 6 episode 11):

A foal tells other foals he heard a grown-up curse, and after they gather around him, he tells them the curse word... and it's "peeved", or something equally innocent. Then, after you laugh thinking how innocent that is, a grownup overhears and is shocked, and scolds the foal, giving a second laugh (though it's hard to explain exactly why that's funny; please explain it to me if you can).

I think this story came out before season 6, but am not sure. I want to use it as an example when talking about how comedy works by upsetting expectations.

I like the MLP show version you linked to above. It's short.