It took Mean Girls fans '20 years' to finally work out major punchline in film leaving them mind blown

It's finally that time of year again, gals.

Yep, it's October 3rd today which is unofficially 'Mean Girls' day given the iconic moment protagonist Cady Heron, played by Lindsay Lohan, started talking to her crush Aaron Samuels (Jonathan Bennett) 'more and more'.

In a voiceover montage chronicling this coming-of-age endeavour, Cady says: "On October 3rd, he asked me what day it was," to which it pans to her responding in real time.

"It's October 3rd," she replies - comedic gold at its finest if you ask me.

It's Mean Girls day today! (Paramount Pictures)

The iconic Tina Fey-written chick flick, which shaped many of our childhoods, first hit our screens yonks back in 2004.

And while it's maintained a dedicated and loyal fanbase over the decades, it's surprisingly taken some fans a whopping '20 years' to finally work out a major punchline which has blown their minds.

One scene saw Cady and the Queen Bee, Regina George (played by Rachel McAdams) discuss her former friendship with Janis Ian (Lizzy Caplan).

"Let me tell you something about Janis Ian," Regina began. "We were best friends in middle school."

Regina told Cady an anecdote about Janis allegedly being a lesbian (Paramount Pictures)

She went on to claim Janis was 'jealous' of her boyfriend at the time and was totally 'obsessed' with her.

"So then for my birthday party, which was an all-girls pool party, I was like 'Janis I can't invite you because I think you're a lesbian'," Regina said.

Continuing the extremely homophobic rant that clearly hasn't aged well one bit, Regina jabbed: "I mean, I couldn't have a lesbian at my party!"

However, one Mean Girls theory claims that Janis never actually told Regina she was a lesbian but in fact that she was 'Lebanese' after mentioning at the end of the film that she's Lebanese while hanging out with Kevin G.

Since making the bombshell discovery, fans rushed to social media to share their reactions.

One X user admitted: "My dumba** just realised in Mean Girls everyone thought Janice Ian was a lesbian because they misheard her say she’s Lebanese and that’s the joke."

Mean Girls fans shared their theory on the hidden punchline (Paramount Pictures)

"It took me nearly 20 years, but I finally made the connection of the Janice Ian Lesbian/Lebanese joke in Mean Girls. Thanks," penned a second.

Other die-hard fans of the iconic series were clearly already in the know, with a third X user explaining: "In Mean Girls Janice gets asked if she’s Puerto Rican & replies no she’s Lebanese.

"Earlier in the movie Regina says she stopped hanging out with Janice cos she’s lesbian. So the entirety of mean girls happened cos Regina didn’t know the difference between lesbian and Lebanese."

Take a look at the scene here:

"Isn’t the whole joke of Mean Girls that Janice is Lebanese and not a lesbian…" pointed out a fourth.

Another praised: "The best part of Mean Girls will always be them thinking that girl was a lesbian bc she’s Lebanese."

And a final user echoed: "Mean Girls is way funnier now that we know Regina George thought Janice was a lesbian & not Lebanese like she told her."

I guess you really do learn something new every day!