Viewers Spot Small Plot Detail That Explains Why Kevin Was Left Behind In Home Alone

And if the prospect of being eight and spending a Christmas all alone isn't traumatising enough, poor Kevin ends up having to defend his family home from the 'wet bandits' - aka Harry and Marv, a couple of clueless burglars who are dead set on breaking into the McCallisters' gaff.

Now, if you're wondering how on Earth a family manage to fly all the way from the US to France without realising they've left their kid behind then you're not alone - but there's more than just terrible parenting at play here.

Because in one of the very first scenes in the flick, the entire family are sitting down to have their tea when Kevin gets into a bit of a scrap with his brother Buzz.

In the course of their scuffle, some fizzy drinks get knocked over and soak the plane tickets and family's passports.

Kevin's dad steps in and cleans up the mess with some disposable napkins, which he then dumps into the bin.

But as the camera focuses on the bin Kevin's plane ticket can be seen among the rubbish, after it was accidentally lashed out with the dirty napkins.

It's a blink and you'll miss it moment, but you can see it here in this screenshot:

The next day, shortly before they head off to the airport, a small kid who is having a great time riffling through their belongings, is accidentally included in the head count.

This helps to explain how the family managed to board a plane and fly thousands of miles before realising that the little fella had been left behind.

Taking to Twitter after spotting the plane ticket, one person said: "I have seen Home Alone probably 1 billion times, but was today years old when I realised they threw out Kevin's plane ticket during the pizza debacle and that's why no one figured out he was gone earlier at, like, the airport."

Another person wrote: "Watching Home Alone for the 50th time and I've never noticed that in the starting scene when there is a fight in the kitchen, Kevin's ticket is put in the bin. Who knew?"

Still, at least he made the best of a bad situation by torturing a couple of relentless burglars.

Merry Christmas, ya filthy animals.