Most inappropriate age-to-content movie I saw was Don't Be a Menace to South Central While Drinking Your Juice in the Hood. Watched it at my friend’s house at a sleepover with his older sister and her friend. We were 10, they were 16. I don’t think I understood 70% of the movie at the time but his sister and her friend were gorgeous so we could have watched paint dry for all I cared
Also saw Event Horizon at a hockey tournament with a bunch of teammates in one of the hotel rooms while the parents were hanging out at the hotel bar. I was 12. That movie fuuuuucked me up for a while, I was only able to watch it again 20 years later or so and while it’s still disturbing, it obviously didn’t affect me like I did when I was 12.