Home Alone fans notice major mistake in movie that suggests Kevin wasn’t the only child left behind

Gathering around the TV with your family and loved ones to watch old movies is as much a part of celebrating Christmas as decorating the tree or sipping on egg nog, even if everyone's watched them dozens of times.

Even though many people will think they know every scene of festive movie classics like Elf or It's a Wonderful Life , eagle-eyed viewers have spotted a hidden detail in one of their favourite Christmas films that they had never noticed before.

This year marks the 35th anniversary of what is now a staple of the holiday season, people gathering to watch the Christmas classic Home Alone and Macauley Culkin's iconic performance as eight-year-old Kevin McCallister.

But this tale of outright child neglect by two parents who are more concerned with chugging champagne and flying first class than correctly counting their kids, contains a howling error in it that might mean that Kevin is not the only one who has been left at home.

Kevin was not the only child abandoned in the first 'Home Alone' (20th Century Fox)

For the singular person out their who has not seen this Christmas gem, the film opens in the McCallister's luxurious Chicago home as Kevin's family and his cousins gather before their trip to Paris. But after getting into a fight, Kevin is sent to bed early.

After oversleeping the next morning, Kevin's neglectful parents Kate and Peter manage to make their flight, but miss that their son is not on the bus, at the airport, or even on the plane. At the same time, two burglars attempt to break in and steal the family's valuables, something that Culkin's industrious character plots against.

Some Home Alone superfans have already clocked that Kevin would never have been able to get on the flight anyway, due to a subtle detail at the start of the film.

When Kevin gets into an argument with his brother Buzz over a pizza, their fight sees a drink spilled onto the kitchen counter. When all of this is cleaned up, their youngest son's plane ticket can just about be seen in the trash.

Culkin was just 10 when he starred in Home Alone (20th Century Studios)

This is why they did not notice that they had one too many tickets. Although, with another detail in the film implying that another child has been left behind in the cold, it is clear that the McCallister adults should not be responsible for anything.

Another fateful moment in the film's opening scenes where Kevin's absence could have been spotted is when cousin Heather is doing a headcount for the children getting off the bus.

As she is walking down the line of kids counting them with a pat on the head, Buzz begins shouting random numbers to put her off. This causes Heather to count herself twice, patting herself for both number three and 11.

Thinking she has done her job properly, when Kate asks her if everyone has been counted, Heather replies: "11, including me. Five boys, six girls, four parents, two drivers, and a partridge in a pear tree."

But this implies that, with Heather counting herself twice and 11 is the total number of kids, another member of the McCallister clan has been left behind somewhere.

Home Alone fans on Reddit have taken this error half seriously, with one saying: "It makes me think there's another McCallister kid frozen under a bush somewhere that they didn't even realize."