Spoilers - So the explanation for the janitor character..

I suspect he didn't speak because he was probably being paid by the word.

Agreed I'd have liked some explanation as to why he didn't talk. I assumed he was PTSD or something I don't kniow. I also kept cringing every time he would crush those soda cans etc. Also like how was he [spoiler]Expecxting to raise that girl[/quote] when he coulden't even speak. Silence is consent I guess when she got in the car.

Imagine thinking a movie as silly as this requires any explanation.

I agree... Especially about the timer thing and his need to drink a pop... I can better accept not explaining him talking and even being able to kill the monsters as it does seem to me everybody should be able to kill them if they just tried...

Some SPOILERS below.

I found myself over-analyzing it. I started thinking, "Is he able to defeat the monsters because he followed the rules?"

Hear me out, but what if Tex inadvertently casts spells? The serial killers use a Satanic ritual, so invoking magic like that in movies often leads to letter-of-the-law magic effects. What if part of their power comes from Tex, in a way? When Tex gives those "rules", and binds the victim with "You are officially on staff," maybe they're responsible for the animatronics (ie, only allowed to fight in self-defence), and they have to follow those rules. But, if they do follow those rules, the demon puppets aren't as powerful?

Or maybe there's something in the movie's themes here about hard work and discipline. The teenagers are all over the place, can't formulate plans, make irrational decisions, fail to act according to any discipline at all, and they get (mostly) wiped out. The Janitor has discipline, follows the rules, takes breaks, cares for himself, etc., and he mows them down. Maybe it's not a magic effect, per se, but a commentary on work ethics?

I was thinking that maybe he survived one of the family attacks as a kid and that is why he doesn't talk.

Sometimes it is best when a director leaves it up the audience's imagination. Do we really want to know what was in Marcellus Wallace's briefcase?

Let's see - He follows some unseen rules to the letter, disregarding the safety of others when for example his alarm goes off.
He is seemingly superhuman compared to all others while fighting the monsters.
He says nothing to anyone

I would guess the idea behind this setting is that The Janitor is supposed to be a player-controlled character and the others are NPCs in a computer game. The inspiration behind the movie is also a game, so shouldn't be too far fetched.