If you haven’t read it yet. 
Dana Carvey made his movie debut in this movie playing an assistant. He can be seen receiving instructions from a blond reporter in front of the Wallace house.
The film is set immediately after the first Halloween (1978). Since Jamie Lee Curtis had begun to wear a much shorter hairstyle in the 1980s, she had to wear a wig that matched her original hairstyle for the film.
Halloween II was originally written to take place in a high rise apartment building. Later in script meetings, however, the setting was changed to Haddonfield Hospital.
This is the only Halloween film to show the morning after the 31st, every other movie ends on Halloween night.
John Carpenter turned down an offer to direct, but remained involved with the production by writing the screenplay.
Pamela Susan Shoop (Karen) got an ear infection during filming of her death scene as the water in the hot tub was apparently “none too clean”.
Believing Rick Rosenthal’s version of the film to be too tame, John Carpenter shot a few gory scenes that were added into the film despite Rosenthal’s objections.
The scene where the Boom Box Boy, played by Lance Warlock, runs into Michael in Haddonfield town square was shot on one of three nights of re-shoots done by original Halloween (1978) director John Carpenter.
The voice of Alice’s friend (heard over a telephone) is the voice of Nancy Kyes, who played Annie in Halloween (1978), and appears in Halloween II (1981) as the corpse of Annie.
The 17-year-old who was hit by the police car and burnt alive, at first believed to be Michael Myers, was supposed to be Ben Tramer, the boy Laurie confesses to have a crush in in the original Halloween.
Ben Tramer, who gets killed, is a reference to John Carpenter’s friend Bennett Tramer. They went to USC (University of Southern California) as Tramer wrote episodes for ‘“Saved By the Bell” (1989)’.
Dick Warlock wore lifts in order to appear taller.
The film that the security guard and the Elrods are watching is Night of the Living Dead (1968).
In the scene where Michael tries to attack Laurie as she’s climbing through the window the scalpel that he’s holding was actually just an eraser on a stick.
As revealed by the Sheriff’s Deputie’s patch, Haddonfield supposedly exists in Warren County, Illinois. Warren County is actually in Nothwest Illinois. Warren County more likely refers to the county in Kentucky which contains the city of Bowling Green where John Carpenter grew up.
Alice’s friend Sally (the girl on the phone in the beginning of the movie) tells her the murders happened on Orange Grove. This is the actual name of the street where this film and Halloween (1978) were filmed. The houses that portray the Wallace and Doyle houses are on Orange Grove just north of Sunset Blvd in Hollywood, California
John Carpenter spent time growing up in Bowling Green, Kentucky, and there are several references to Bowling Green and the surrounding area: Smiths Grove and Russelville are towns nearby; Bowling Green is in Warren County, where Haddonfield is set; and Elrod, Chestnut, (31W) Bypass, and Scottsville are all names of local streets in Bowling Green. Additionally, someone in the film makes a reference to the Lost River Drive-In, which was a real drive-in theater in Bowling Green.
Was filmed at Morningside Hospital, 8711 South Harvard, Los Angeles which had recently closed and has since been torn down.
Anne-Marie Martin came into production as a favor when additional footage was being shot. John Carpenter shot the scene that involved Martin and supporting cast member Pamela Susan Shoop.
The only Halloween film to be produced by Universal Studios. After the massive success of the first film, Universal picked up the sequel. When the sequel didn’t fare so well, Universal gave the rights to Trancas International , an affiliate of Universal’s, who produced the films until 1989. In 1996, the rights were sold to Dimension.
The mask Michael wears is the exact same mask (a repainted and modified Captain Kirk mask) worn in the original film. It looks different in the sequel because the latex had decayed in the years between films, and Dick Warlock is shorter and stockier than Nick Castle, so the mask fit his head differently. All the subsequent sequels used different masks that looked rather different.
Continuity: In the Ben Tramer scene, when the police car hits Ben and smashes into the white van, Ben is slumped over the police car. When the close-up of the crash seen is shown, he is seen leaning against the white van.
Revealing mistakes: When Dr.Loomis and Sheriff Brackett are in the car, one of Brackett’s police officers call in on the radio. Many times throughout their conversation, the man on the radio talks before Brackett lets go of the button
Factual errors: When Michael corners Laurie in the elevator, the door slams on his hand and keeps closing. Elevators have rubber guards that cause the door to open again if someone’s hand would get caught in the closing.
Audio/visual unsynchronized: After Michael is shot in the eyes and blinded, he starts swinging the scalpel wildly at Loomis and Laurie when they start releasing the gas. As Laurie flees before Loomis lights the place up, the sound of Michael swinging the scalpel is out of synch by around half a second when he actually does swing it.
Continuity: After finding the head nurse dead, Jimmy turns to leave the room and slips in the blood and gets it all over his face and jacket. When we next see him in the car, there is no blood on his face or clothes.
Revealing mistakes: When Janet spins the dead Dr. Mixter’s chair around, his right hand flinches.
Errors made by characters (possibly deliberate errors by the filmmakers): Dr. Loomis and the policemen find the word “Samhain” written on the blackboard at the elementary school, and Loomis claims he knows the meaning of the word, delivering a speech about the “festival of Samhain”. However, he pronounces the word literally, which is incorrect. It’s actually pronounced “sow-in”.
Audio/visual unsynchronized: In the climactic scene in the operating room, Laurie says “Michael, stop!” before shooting him, but her mouth does not move.
Revealing mistakes: Laurie fires two shots and supposedly shoots Michael directly in each eye, yet when he looks up and blood streams down from his mask, we can see his eyes are intact.
Continuity: Near the film’s climax, the Marshall is shown walking down a hallway by a soda machine and reacting to Laurie’s screaming. Several minutes (and many screams) later, Michael crashes through the door and the Marshall is still running down the hallway by the soda machine.
Continuity: Dr. Loomis says that Michael is 21 years-old, yet when the credits appear at the end his age is given as 23.
Continuity: Dr. Loomis shoots out the passenger window of the Marshal’s car, but it is intact in later scenes.
Continuity: Jimmy passes out lying in a pool of blood, but later in the car there is no blood on him anywhere.
Factual errors: Doctor Loomis fills the room with flammable gas. He then lights a lighter that makes a flame, hesitates, and then ignites the gas in an explosion. The same sparks that ignited the lighter fuel would have ignited the flammable gas simultaneously.
Continuity: When Officer Hunt calls for backup at the Meyers’ House he says that the address is “45 Lampkin Lane”. The address on the house is 709.
Continuity: In Halloween (1978), Michael falls off the back balcony of the Doyle house, however in this film he falls off the front balcony. The balcony in the first movie is a covered balcony, the balcony in this film is not.
Continuity: At the beginning of the movie, the front door lights on the Doyle house are on and off depending on the scene.
Revealing mistakes: Other than a patient that Jill responds to, no other patients are ever seen or heard throughout the large hospital, despite the fact that the maternity ward has several newborn babies.
Anachronisms: Set in 1978, some of the clothing and hairstyles have noticeable characteristics associated with the early 1980s; particularly those of Alice, Karen, and Darcy.
Revealing mistakes: As Michael is falling off the balcony of the Doyle House after being shot by Dr. Loomis, you can see the ramp through the railings that’s assisting the stunt man.
Factual errors: The film takes place in Illinois on Halloween, but you’d never know it looking at the colors of the trees, they are all a healthy green.
Continuity: It’s supposed to be a continuation of the same night from Halloween (1978), yet the landscaping for the Wallace and Doyle houses has changed considerably. Also, the jack-o’-lantern on the front porch of the Doyle House has changed completely.
Plot holes: Considering how immense Haddonfield Memorial Hospital is (it has wings), and the fact that it has an emergency room and surgical ward, it should not have just four nurses, one doctor, and two ambulance drivers staffed for the entire hospital, even if it is the night shift.
Audio/visual unsynchronized: If you listen closely, you can hear the faint sound of the buzzer for the nurse’s call button before it actually goes off in the film (this happens twice).
Revealing mistakes: When Sheriff Brackett looks at the dead body of his daughter, Annie, her eyes twitch just after he closes them with his hand.
Continuity: Just before the sheriff closes his dead daughters eyes outside the house, he pulls the blanket covering her down to her chest, just after he closes her eyes the blanket is pulled right up to her chin.
Continuity: The flashing lights on the front of Bud and Jimmy’s ambulance change places as they pull into the hospital driveway. They go from either side of the hood to the front of the bumper.
Continuity: When Nurse Karen is shown for the first time in her uniform, her belt is a dark tan. Subsequent shots of her in the uniform show a white belt.
Continuity: When Budd goes to check on how hot the water is, he rubs condensation off the gauges, but there wasn’t anything on them to begin with.
Crew or equipment visible: On the widescreen DVD, when the hospital room blows up, you can see around the set wall twice for about a second each time.
Crew or equipment visible: At the hospital, you can see the camera in the Marshall’s mirror.
Continuity: At the beginning of the film when the old man is watching Night of the Living Dead (1968), the film skips five minutes in about a minute.
Crew or equipment visible: When Sheriff Brackett is trying to stop Dr. Loomis from shooting Ben Tramer, the shadow of the cameraman falls on Dr. Loomis’ overcoat.
Continuity: Brackett closes his door as he runs after Loomis in the street. When he’s trying to stop him from shooting Ben Tramer, the door is now open in the background.
Continuity: Laurie gets into the elevator from the basement level. As soon as it closes, the other side opens. She walks out and she’s back on the ground level.
Continuity: The word “Sheriff” on the front of Sheriff Brackett’s police car.
Continuity: When Laurie is wheeled into the ambulance, the blanket on the stretcher isn’t covering her feet, but when the paramedics lift her out of the ambulance, the blanket covers the whole of her feet up.
Continuity: At the beginning of the film Michael’s hair is all puffy, but when we see him walking towards the hospital, it is all flat and combed back.
Continuity: The blood on the chopping board at the beginning of the film.
Factual errors: Marion calls for help on the police car’s 2-way radio, then listens to the reply without letting go of the “talk” button on the radio’s microphone. You can’t listen and receive anything on the radio while the button on the mic is pressed.
Continuity: The security guard is sent to find the reason the phones do not work in the hospital. A couple of scenes later, you see a nurse chatting on a hospital phone.
Continuity: After the explosion and Michael is walking on fire, he is right next to the burning stretcher. The next time we see him, he is about eight feet behind the stretcher walking towards her again.
Continuity: When Gary and his mother arrive at the hospital, the ambulance containing Laurie can be seen driving up in the background. In the next shot, the ambulance enters the parking lot and drives up behind them again.
Revealing mistakes: Pieces of foam from the fake door Michael smashes through can be seen raining down in the gas room.
Continuity: Jimmy’s position as he slips in the pool of blood.
Continuity: Laurie is on the ground beside Jimmy’s car outside the hospital when she sees the Marshal’s car pull up. When Loomis tells the Marshal he ought to handcuff him to the wheel, Jimmy’s car is visible in the distance but Laurie is gone.
Anachronisms: The film takes place in 1978, but the ambulance has rectangular headlights, which were not introduced on full-size Ford vans until the 1980 model year.
Continuity: Dr. Mixter’s coat changes position on his left shoulder when Laurie is in the emergency room
Continuity: Near the beginning of the film, when Michael walks into the Elrod house, Mrs. Elrod is seen standing in front of the door from the kitchen to the living room, and when Michael picks up the knife, she’s seen standing to the side inside the living room.
Continuity: When Michael stabs Nurse Jill in the back with the scalpel and lifts her off the ground, her shoes fall to the floor and rearrange themselves seconds later.
Continuity: When Michael is drowning Nurse Karen in the scalding water, her towel goes from being wrapped right below her shoulders to tied around her waist between shots.
Factual errors: Water at 125 degrees Fahrenheit is not hot enough to scald a body. Minimal effects usually start at about 140 degrees.
Continuity: In the ambulance, Jimmy tells Laurie they’re taking her to “the clinic”. The radio announcer also reveals that Laurie was taken “across town to Haddonfield Memorial Clinic”. However, the jackets that the medics wear, as well as all the signs at the hospital, indicate that it’s actually Haddonfield Memorial Hospital.
Continuity: Jill turns around to find Michael Myers behind her just before her death but when he stabs her she is facing forward.
Continuity: Jimmy walks across a puddle of blood before finding Mrs Alves. When he slips, you can’t see any footprints.
Continuity: When the first close-up of the ambulance is seen driving up to the hospital, you can see on its front bumper that it does not have red flashing lights. However, in the next shot, it has 2 red flashing lights mounted on the front bumper.
Revealing mistakes: When Michael is hiding in the nursery, it is obvious that the “baby” closest to the camera is a doll.
Revealing mistakes: At the end, as Michael emerges from the explosion, his body embraced in flames, one can easily tell that the clothing the actor is wearing is much thicker all over and now includes gloves that the character Michael was not wearing before.
Factual errors: Diethyl Ether was supplied for anesthesia in liquid form in 1/2 liter metal bottles. It is never put in gas cylinders as shown the the final OR scene.
Errors made by characters (possibly deliberate errors by the filmmakers): Dr. Loomis pronounces the word ‘Samhain’ as ‘Sam-Hain’. This is an incorrect pronunciation. ‘Samhain’ is an Irish word and is pronounced ‘Sow-in’, the m+h make a ‘w’ sound.
Errors made by characters (possibly deliberate errors by the filmmakers): Laurie bangs on the hospital door for about 30 seconds before Loomis lets her inside even though Koomis was standing near the door the whole time.
Revealing mistakes: When Michael sticks the syringe in to the nurse Janet’s eye and pushes the plunger, her eyes never even flinch.
Continuity: At the beginning of the movie, it is mentioned several times (on TV on the radio and in telephone conversation) that 3 teenagers were killed, but then police discovers the bodies only after that - which we learn in the conversation between Sheriff Brackett and his deputy who tells him they have just discovered 3 bodies “in the house across the Doyle’s house”, and that his daughter was one of them.
