The movie that comes to mind for me is Matango. It's a 1963 Japanese horror film by Ishirô Honda (the director of the Godzilla movies) that IMDb describes as "Shipwrecked survivors slowly transform into mushrooms.".
I was curious what other PG horror movies people like. I find a lot of the time the limitations or target of an age rating can become noticeable and distracting.
I remember the audiobook of Coraline scaring the living bejessus out of me as a kid, way moreso than the movie. I do love the movie though, it's so good
Does "Jaws" count? It wouldn't be PG these days but I'd say it counts as horror.
"The Birds" was technically unrated when it came out. I've seen it rated as PG-13 now, but not sure what that's based on since it is from way before PG-13.
The MPAA rating system didn't start widespread use until the early 1970s, and even then (as you'd expect since since it is the MPA"A") only in the USA. Other rating systems in other countries followed later (for the most part).
So any movie prior to that would have been unrated when it came out. Especially if it was a non-USA production.
Any rating you see on a movie older than that has been applied after the fact.
Poltergeist. Only PG rated horror movie I actually still think is a little scary. Every time I have meat, I can't help but think of that scene with the maggot steak, followed up by the face peeling. 🤢
I think that's a fantastic description for Willy Wonka. I remember as a kid watching the boat ride scene and thinking "is Mom sure this is a kid's movie‽"