The Grinch fans reckon film is ruined forever after spotting NSFW moment

From cult-classics to modern spins on the genre - it's clear many of us love a good Christmas movie.

And after you've rattled through the rom-coms like Love Actually and The Holiday all the way through to Home Alone and It's A Wonderful Life - you'll, no doubt, be turning your attention to How the Grinch Stole Christmas.

The comedy-fantasy first hit our screens back in 2000 starring the likes of stars Jim Carrey as the Grinch himself with Taylor Momsen, Jeffrey Tambor, Christine Baranski, Bill Irwin and Molly Shannon in supporting roles.

Some armchair critics, however, have seemingly spotted a pretty cheeky NSFW reference in the Christmas fan-favourite. Have a look:

The movie follows the Grinch, who lives in solitude just outside Whoville, and hates the townsfolk and despises Christmas when Cindy Lou, a six-year-old girl who believes in the spirit of the festival, sets out to reform him.

Rated as a PG, fans reckon How the Grinch Stole Christmas slipped in the X-rated reference which clearly passed us all by the first time-around.

The reference in question takes place in the scene when the little Grinch is peeking through the window as the people of Whoville start to arrive at their 'annual holiday get-together'.

My face after clocking the swinging reference (Universal Pictures)

As the Whos walk through the front door, they drop their keys into a round glass bowl.

Now, that may not have seemed even the tiniest bit risqué but here's a little context that may make you think otherwise.

Way back when in the 80s, there was a popular craze for 'wife-swapping' parties.

Such motives were also referred to as 'key parties' as the group events would see couples popping their keys into a communal bowl, which were then randomly handed out, determining which couples would have sex.

Fans of the flick clearly couldn't wait to share their shocking discovery with one tweeting: "So is it me or did we just put our blinders on when The Grinch Stole Christmas introduced us to wife swapping parties? Lol."

Fans reckon the keys in the bowl was a cheeky reference to swinging parties (Universal Pictures)

A second quipped: "What baby Grinch witnessed when he was stuck in that tree was a whole a** wife swapping party HUH."

"Ok this will ruin your Christmas video watching. In The Grinch That Stole Christmas, the story is based on a wife-swapping party AKA a 'key exchange party'," declared a third.

A fourth chimed in: "Yup. Still obsessing over the Whos being wife-swapping swingers in the Jim Carrey Grinch movie."

"LMAO love how the Whos are blatantly having a wife-swapping party in the Grinch. Some kids film this is!" echoed another on X, formerly Twitter.