Question: How can Michael recognize Laurie as his younger sister since he wouldn't have seen her since she was only two years old?
Question: Why aren't there any other patients/staff?
Answer: I have read that, in early drafts of the script, the hospital was a health clinic, not a standard hospital. This would possibly explain why there are only a small number of patients, though it doesn't explain why there is a maternity ward, or why the mother brings her son there for emergency treatment.
Answer: Apparently there were quite a few patients at HMH. If you remember the scene where Karen was putting pills into individual cups just before the room buzzer goes off, in which she finds Bud under the sheet, there are many of those cups. Also we know for certain there was a patient named Ms. Carr who was supposed to receive attention at 9:30 the next morning, told to Karen by Ms. Alves, while Michael was standing in the rear of the nursery area watching them. And of course there were all the newborn babies, leading me to believe there were a few new mothers in the hospital as well.
This could possibly be the "best" answer to a question that I've ever read. But seriously, I had wondered the same question 35+ years ago and this reply made me think of things I hadn't thought about. That empty hospital was actually quite crowded.
Answer: One could argue that Haddonfield is a small town, and perhaps there just aren't that many doctors, nor that many patients in the hospital at any given time. It really just depends. Also, I've had to go to the ER a number of times in my life. Most of the time, it's busy, but there has been a few times where it has been pretty much completely dead and empty, not too dissimilar from what you see in this movie. So it could possibly just be a slow night.
Question: Did Dick Warlock play Michael Myers in every scene he's in, even stunts? I was curious considering that Warlock was a stuntman and could have done the balcony fall and Michael burning scenes as well.
Answer: From what I have read: yes.
Question: Why does Michael waste time leaving "Samhain" on the blackboard and killing all those hospital people? He's able to slip all over the place so all this extra killing seems pointless.
Answer: Michael is insane. It's no different from him killing all the people in the first movie and setting up all the elaborate things he set up like the tombstone and the bodies. In the context of the movie, he's simply driven to kill and do evil things on his way to his goal.
Question: Why would Laurie ever go and visit Michael in the asylum?
Answer: Maybe she wanted to see her brother and was too young to "understand" the severity of what he did? Maybe her adoptive family thought it would be good for her to try and have some sort of relationship with her brother so they took her to visit him? Etc. Pick your poison. There's any number of valid reasons why the relative of a criminal might go to visit their family member in prison or an asylum.
Answer: She didn't, the movie picks up were the first one left off, on the same night. She went directly to the hospital and stayed there all night.
No I mean when she's in the hospital. She dreams that she's visiting him at Smith's Grove.
Answer: There is a scene where Laurie dreams about meeting Michael as a young teen. It's unknown whether this is an actual memory of real events, but since nothing indicates otherwise, we could assume the he saw her at an older age when she looked closer to her 17-year-old self.