Robin Williams feels like an ENFP but his character in Dead Poets Society feels more like an ENFJ...(to me)...
I understand your point about the difference between caring and bubbly...ENFJs come across as more parental whereas ENFPs more childish...
I've always imagined PolyAnna to be someone like this though:
It's easy to see her that way, hahahaha.
I watched "Dead Poet's Society" again today, and I have to agree that Robin Williams seems more ENFJ in the movie, my memories about him were really clouded. It was a long time ago when I watched it, and I had little understanding about MBTI+enneagram at this time (I was around 14, discovering the system yet, a noob). But he's certainly an ENFJ 7, what gives him some ENFP vibe, and Pollyanna is probably an ENFJ 2, and it makes the difference between them.