These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Memetic Mutation: The first of the two famous spoilers is almost a Stock Parody now, with a nervous individual tightening the grip on their blanket and whispering out any number of variations: "I see white people" "I see dumb people" etc. It even named a trope.
Rewatch Bonus: Very worth a second look once you've seen the end.
Seinfeld Is Unfunny: Believe it or not, before "the Shyamalan twist" became a requisite part of M. Night Shyamalan's movies (and before they became rather infamous for not making any sense), this movie's Twist Ending was genuinely unexpected, and even Shyamalan's detractors are generally willing to admit that he pulled it off quite well. Some would even argue that it led the directors of similar psychological thrillers to copy Shyamalan by shoehorning twist endings into their movies at the expense of plot and character development, further diluting this movie's impact.