Michael drops his knife after being stabbed by Laurie with the knitting needle. Later, he is seen attacking with the knife, but the knife he dropped is still sitting on the floor near the couch in the closing montage. This is explained in an earlier scene where Sheriff Bracket says that "a Halloween mask, some rope, and a couple of knives" have been stolen. Michael had more than one knife on him throughout the night.
When Michael Myers murdered his sister Judith on Halloween night, he was dressed up in a clown costume. You might wonder if that means anything. It does, because that makes him a Monster Clown, and clowns have had a long history of existing and behaving outside the rules. That's right, Michael is essentially The Joker of slashers, engaging in random killings and behaviour from childhood!
Plus, psychopaths and sociopaths also have a history of behaving outside the rules, and Michael is definitely one or the other.
Even funnier when you take into account that originally, the film's production had found two different masks for Michael to wear. Other than the William Shatner mask that ended up being modified and used (and becoming iconic), the other was a scary clown mask that Tommy Lee Wallace thought that John Carpenter would go with. And twice as funny when Michael does end up wearing such a mask later on in the series (Halloween 5: The Revenge of Michael Myers) for one scene.
How will the Wallaces react when they discover that three teenagers were murdered in their house? As well as the family dog!
Annie's shirking of her babysitting responsibilities probably saved Lindsey's life in the long run. While we don't know that Michael would kill children, he shows no problem killing animals, and anyone who gets in his way. So had Lindsey stayed in her house, she probably would have been killed too.
As we learned in Halloween (2018), yes, Michael does in fact kill children. So, Annie did inadvertently save Lindsey's life.
When Lynda is killed, her final thoughts must be that Bob, her boyfriend, is the one attacking her. She never saw Michael Myers, and just assumed that he was Bob in a sheet ghost costume playing a trick on her. She then turned her back to make a call, and Michael murdered her with the phone cord before she saw him. I suppose it doesn't make a tremendous difference either way, but still, the poor girl thought it was her boyfriend strangling her to death.
When Michael escapes, he lets out a bunch of patients who acted like harmless, drugged-out zombies. But Michael can't be the only murdering psychopath in the place, right?.
Many people find it odd that Michael seems to take his time between Laurie getting out of the Wallace house to the Doyle house (stopping at the next door neighbors in an attempt to get help) instead of being hot on her heels (which is something that happens in Zombie's remake of the first film). But when you take into account the earlier scenes in the film, you realize Michael enjoys stalking his victims, not just killing them. That would explain why he held back and let Laurie run for the neighbors house before getting over to the Doyle residence. He's enjoying watching her struggle and call for help before moving in for the kill.
