I learned a lot watching Sesame Street as a child, and by watching and re-watching it as an adult, I'm still learning things about pedagogy and about comedy and about faith in humanity. But as a kid, there was only one time I was actively aware of what I was learning while watching Sesame Street.
I don't specifically remember how old I was, probably about four or five, when I saw this insert for the first time. I'll summarize it: two white boys are playing cowboys & Indians, and the boy playing the Indian is talking in a really exaggerated, Hollywood "Injun" accent (for lack of a better term), and another boy comes by and tells them, "Indians don't really talk like that," and the other boys say, "Oh yeah? Well, how do you know?" and he says, "Because I'm an Indian."1
I remember that the realization struck me like a bolt from the blue: "Oh, so Indians are just regular people then." Somewhat embarrassingly, that idea had never occurred to me until that moment. But I never forgot it, and I guarantee that I'm a better person because of it.
1In the '70s and '80s, it was still common practice to refer to the indigenous people of North America as "Indians," even though everyone knew that it was inaccurate. I remember that I never heard the term "Native American" until I was in first grade, which was 1987-88, and at that point I had no idea what it meant. To this day, it still throws me for a loop when people correctly use the term "Indian" to refer to people or things with origins in India; I tend to refer to them as "Indian-from-India" to preemptively avoid any confusion.