When my step-dad first saw MI, he was under the impression that even though all the audience and the monsters saw was Boo’s bedroom, she actually lived in a house and had parents. At the time, I thought he was reading too much into the film, but it raises a good question: Does Boo have parents and how do you think they felt once she entered Monstropolis?
I wouldn’t think he was reading too much if I were in the same position. Boo had to have had parents to even be born, and to have room she had to have lived in a house.
Sorry if I sound…belittling at all…
Many people want to know about Boo’s parents. An especially good note is that Boo was gone for practically 24 hours, completely absent from her room, her house, her neighborhood, her WORLD. How would parents feel about THAT and what would they do when she suddenly appeared out of nowhere?
Personally…Boo’s parents could be anything. But if I had to guess…they were…loving. MAYBE they were those “really busy parents” that nurtured on the side…but…
I think they were fair enough parents, doted their daughter (but didn’t spoil her). She may be an only child or at least the youngest of siblings…
How they felt about her disappearing? Well the natural reaction would be panic. Heck, if they heard all of Sullivan’s thumping (if they were there, some believe a babysitter was instead)…and suddenly go to her room to find her gone, they may have thought she was kidnapped.
No, not belittling. But it’s important to bear in mind that I’m a very literal person. If I don’t see her parents or hear that they exist or see any other rooms of her house, then what else do I have to go by? Plus, I was thirteen when I saw MI for the first time; I didn’t comprehend certain things like I do now.
Completely understandable. And in some ways, some people don’t tend to think outside the “box of the movie” and just focus on it’s enjoyable 1-3 hours of entertainment. Sometimes takes a bit to consider some things that weren’t touched upon or thought of before.
I kind of assumed that the flow of time is slower in the Monster World than it is in the human world- what was 24 hours for Sully and Mike may have only been a couple of hours in Boo’s house. So her parents didn’t notice her absence because they simply didn’t enter her room during the brief period that she was missing for.
I always thought that too. if not that, maybe when you enter the monster world, it’s kinda like you don’t exist in the human world.
i enjoyed the movie!
though these kinda questions do come up! but even the director or the script writer has skipped them!
I’ve often wondered about her parents. And family in general. Where does she live? Does she live with both parents? Does she have sibligns? What’s her real name?
I’m sure that they were freaking out and thought she was kidnapped, by humans. Not monsters. 
Well, we know Boo and her family turn out all right in the end because Boo still lives in the room she was in before, because Sully goes to see her. So we at least know that she wasn’t taken away from her family or something after her mysterious dissapearance.
I agree with Nausicaa’s hypothesis that the implied rational behind timing between the monster world and our (human) world wouldn’t be parallel in time, which would also make it easier for the scarers working in Monsters Inc. to do their job (fitting a, say, 8-hour job with the time zones around the world up to 24 hours).
Also, given that see daylight at the end of the film in Boo’s room, it does imply that the interaction between Boo & Sulley has been restricted to night-time / morning, given that the main storyline in the movie is within a day, which, according to the hypothesis above, is pretty much just overnight - hence, Boo’s parents wouldn’t even know she was “gone” overnight. 
Well, her real name is Mary. And I agree abut time passing slower.