Anybody who's a major film fanatic has loved and grown to remain just as fond of the movie 'The Sixth Sense,' as they were when it came out about 19 years ago. Let's be real and admit that over the years pretty much no other movie - no matter how skillfully crafter - has been able to surpass the plot twist that the M. Night Shyamalan-directed blessed us with. But fans will be surprised to know that the obvious plot twist in the movie - the one that manages to drop jaws even till date - wasn't the only easter egg hidden in the whole hunt. In fact, there is one very fine little, hidden secret that most people have missed on over the years.
*Spoiler alert*
Malcolm being a ghost wasn't the only whopping twist in the movie. The plotline of the spooky masterpiece Shyamalan’s revolved primarily around a troubled young boy, Cole Sear, and his claims of seeing dead people. Bruce Willis as Malcolm Crowe, a skeptical child therapist, eventually realizes Cole has been speaking the truth all along, and by now, as you can predict - he helps the little boy deal with the spirits he keeps getting tormented by.
And like spilled not-so-graciously before, Malcolm is actually a ghost - in fact, one of the many that Cole keeps seeing - which gets revealed by Shyamalan's very skillful panning of the camera to the character's face, thus revealing that Cole was actually saying the truth all along.
There were just minor hints hidden along the massive twist in the end, such as instances of Malcolm wearing the same outfit throughout the movie, or how nobody except Cole seems to be talking to the child-therapist. And it is this very build up to the final reveal that makes it so very thrilling for the viewers.
But then comes the second twist, which is beyond simple mindblowing - and of course, with an even more intense, skillfully led up to its reveal. As Unilad UK points out: Cole Sear knew the whole time that Malcolm wasn’t his child therapist and that he was, in fact, a ghost from the moment he first met him outside his mum’s apartment and ran away from him.
First, of all, Cole seems terrified of Malcolm when they first meet. And you can deduce that it's because he knows Malcolm is a ghost, and not just because Malcolm is a scary looking therapist, from the fact that he doesn't ask his mother who the man is when he sees him for the first time at the door. He doesn't ask her because he knows she can't see him, so he just stands there frozen.

Now, this first hint can also be linked to another major scene in the movie. When the big reveal happens about Malcolm being a ghost, the scene plays out, like:
Cole Sear: I see dead people.
Malcolm Crowe: In your dreams? [Shakes head]
Malcolm Crowe: While you’re awake? [Cole nods]
Malcolm Crowe: Dead people like, in graves? In coffins?
Cole Sear: Walking around like regular people. They don’t see each other. They only see what they want to see. They don’t know they’re dead.
And playing back the scene, you can see that when Cole says the words "they only see what they want to see," he glances down at Malcolm's stomach, looking at what would be possibly Malcolm's gunshot wound, that had killed him. And this is what prompts Malcolm to look down at the spot too, and at that is when he realizes that he had been seeing what he wanted to see, as his fatal wound finally appeared to him.
So this means, in all probability, Cole had seen Malcolm with the bloody wound all along, right from the scene where they first meet. Which would, in turn, confirm, that Cole always knew this was a dead man. Which would make his immediate fear of Malcolm from the very first scene, a lot more rational!
Take other instances for example. At first, when Malcolm asks Cole if he wants to play a game, he just nods in response, and never says a single word. Also when he tells Malcolm that despite being nice, he can't help him, it's not because Cole thinks his problem is beyond the capability of doctors; it's because he knows Malcolm is a ghost and therefore himself is beyond any help.
Director Shyamalan himself answered this question at a fan event, saying 'yes, of course,' and that's all the confirmation you need for now!