Since its debut in 1990, Home Alone has become as much a part of the Christmas cinematic ritual as It's a Wonderful Life. But unlike that uplifting tale about the good of mankind, Home Alone tells a rather unsettling Christmas story of a precocious 8-year-old who, accidentally abandoned by his family, is forced to defend his home from two dimwitted burglars. Kevin McCallister (Macaulay Culkin) turns his family's home into a veritable funhouse of torturous booby traps that so-called Wet Bandits Marv (Daniel Stern) and Harry (Joe Pesci) hilariously stumble through, and the transformation of a suburban Chicago home into a relentless injury machine is nothing short of spectacular. But it does require quite a suspension of disbelief. Can a man really be hit square in the face with a steam iron and walk away unfazed? What kind of permanent physical damage would a blow torch to the head really do? To answer these questions and officially dissolve Home Alone's Hollywood magic, I spoke with my friend Dr. Ryan St. Clair of the Weill Cornell Medical College. Enjoy.

The injury: BB gun to the forehead

The set-up: Marv and Harry try to sneak into the McCallister home by sweet talking Kevin from the back door. Kevin, meanwhile, points his BB gun through the doggie door and directly at Harry's groin — and shoots. When Marv goes to investigate the source of Harry's pain, he is met by the same BB gun, which is fired at extremely close range to his forehead.

The doctor's diagnosis: "Classic air-powered projectile weapons typically have muzzle velocities of 350 feet per second or less. A BB fired at close range from such a weapon could break the skin, but will not penetrate the skull, and is unlikely to penetrate Harry's scrotum, especially through fabric."

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The injury: Iron to the face

The set-up: Thwarted by the BB gun at the back door, Marv runs around to the basement stairwell — which Kevin has deliberately iced. Once he has stumbled his way down into the dark basement, Marv grabs for what he thinks is the light bulb cord. It's actually a rope attached to a steam iron that is propped up on the laundry chute door. The heavy iron comes plummeting down and smacks Marv in the face.

The doctor's diagnosis: "Let's estimate the distance from the first floor to the basement at 15 feet, and assume the steam iron weighs 4 pounds. And note that the iron strikes Marv squarely in the mid-face. This is a serious impact, with enough force to fracture the bones surrounding the eyes. This is also known as a 'blowout fracture,' and can lead to serious disfigurement and debilitating double vision if not repaired properly."

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(Related — Diagnosing Die Hard's craziest injuries: A professional weighs in)

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The injury: Handling a burning-hot doorknob

The set-up: While Marv is getting an iron to the face, Harry tries to enter the home through the front door. The first attempt doesn't go well, as the stocky burglar slips on the icy steps and falls to the ground, landing with a thud on his back. Easing up a second time with the help of the railing, Harry makes it to the front door, reaches for the doorknob — which we see is literally burning red — and grasps the searing handle, the pain of which forces him once again down the icy steps.

The doctor's diagnosis: "If this doorknob is glowing visibly red in the dark, it has been heated to about 751 degrees Fahrenheit, and Harry gives it a nice, strong, one- to two-second grip. By comparison, one second of contact with 155 degree water is enough to cause third degree burns. The temperature of that doorknob is not quite hot enough to cause Harry's hand to burst into flames, but it is not that far off... Assuming Harry doesn't lose the hand completely, he will almost certainly have other serious complications, including a high risk for infection and 'contracture' in which resulting scar tissue seriously limits the flexibility and movement of the hand, rendering it less than 100 percent useful. Kevin has moved from 'defending his house' into sheer malice, in my opinion."

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The injury: A blowtorch to the scalp

The set-up: Unable to get through the front door, Harry returns to the back. He kicks his foot through the doggy door to disarm a potential BB gun threat, delicately taps at the doorknob to test its temperature, and, finding it cool, opens the back door — only to unknowingly arm a blowtorch that fires at the top of his head.

The doctor's diagnosis: "Harry has an interesting reaction to having a lit blowtorch aimed directly at his scalp. Rather than remove himself from danger, he keeps the top of his skull directly in the line of fire for about seven seconds. What was likely a simple second-degree skin burn is now a full thickness burn likely to cause necrosis of the calavarium (skull bone)." That means the skin and bone tissue on Harry's skull will be so damaged and rotted that his skull bone is essentially dying and will likely require a transplant.

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The injury: Walking barefoot on Christmas tree ornaments

The set-up: After surviving the iron to the face, getting his shoes and socks peeled off by tar, and stepping onto a 3-inch nail, Marv abandons the basement entrance and enters the home through a conveniently opened window. Without looking down, however, and still barefoot, Marv jumps in, putting his full weight on a dozen pointy ornaments littered on the wood floor.

The doctor's diagnosis: "Walking on ornaments seems pretty insignificant compared to everything else we've seen so far. If I was Marv, I'd be more concerned about my facial fractures."

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The injury: Paint can to the face

The set-up: Although severely injured, both the burglars are finally inside the house, and have forgone their looting plan for one of revenge. Hearing the taunts of Kevin's pre-pubescent voice, they scamper into the foyer only to slip dramatically on scores of Micro Machines, landing, once again, on their backs. Kevin cruelly mocks them from the top step: "You guys give up yet? Or are you thirsty for more?" Marv and Harry scramble up the staircase, where they are met by a speeding paint can attached to a rope. Harry manages to duck and evade the first hit, but Marv gets a paint can square in the face. Harry continues up the stairs but is hit by a second paint can. Both burglars end up back on the ground floor.

The doctor's diagnosis: "Assuming the paint can is full (roughly 10 pounds) and the rope is 10 feet long, Marv and Harry each take a roughly 2 kilo-newton hit to the face. That is easily enough to fracture multiple facial bones, and is probably going to knock you out cold. Also, I wouldn't expect either of the Wet Bandits to walk away from this with all of their teeth."

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The injury: Shovel to the back of the head

The set-up: Kevin eventually lures the Wet Bandits through his house of injurious horrors, across the street, and into a neighbor's house. But Marv and Harry have clued into the fact that following the little tyke has provided them nothing but pain. They enter the neighbor's house their own way and meet little Kevin at the top of the basement steps. They hang him by his sweater from a hook on the back of a door and outline all the ways in which they will pay him back for the pain he caused, beginning with biting "every one of these little fingers, one at a time." Just before Harry can take the first bite, Kevin's elderly neighbor saves the day, coming up behind the burglars and hitting each one over head with his shovel, knocking them out cold.

The doctor's diagnosis: "Seriously? At this point, Marv and Harry have both suffered potentially crippling hand and foot injuries. Harry has proved to be nearly impervious to burns, and both managed to retain consciousness after taking a flying paint can straight to the face. Suddenly, a frail elderly man appears and weakly slaps them in turn with a flimsy aluminum Home Depot snow shovel. And, somehow, this is too much for them, and they collapse. This movie was way more believable when I was 8."