American Pie fans took over 20 years to discover graphic hidden X-Rated joke

American Pie fans spotted a hidden joke in the film 20 years on from its release and only the most keen-eyed fans would have ever even realised it existed.

The film was arguably one of the most iconic coming of age movies of the 1990s and early 2000s when it released in 1999, leading to three sequels and multiple spin-off films.

Though some may argue that many of the jokes are now problematic and it hasn’t aged well, it is undeniable that the movie influenced a whole generation of teens and coming-of-age comedy filmmakers.

The movie is airing tonight on Channel 4 and fans of the film will be sure to tune in and see the 1999 cult classic and decide for themselves how it has aged.

One of the hidden jokes in the film is actually one of the funniest, as found by fans on Reddit.

For those whose memory is cloudy when it comes to the actual plot of the film, it follows four young male friends who decide they need to all lose their virginity before the end of prom night in their senior year.

Throughout this process, one of the four Kevin is the only one to actually have a girlfriend at the start of things, his perfection-chasing partner Vicky, who is played by Tara Reid.

In a bid to try and make sure their first time is as enjoyable for both of them as possible, Kevin calls his older brother looking for advice.

Bizarrely played by a post-Good Will Hunting but pre-fame and Oscar win Casey Affleck, he points him to a ‘sex bible’ that has been kept secret at the school.

He informs Kevin where to find it hidden in a secret spot in the library he goes and finds an almanac of sexual knowledge that has been kept for decades.

One fan on Reddit noticed an incredibly graphic blink-and-you’ll-miss-it joke.

Posting on the r/MovieDetails subreddit they noticed, just over 20 years on from the original film: “In American Pie the Sex Bible is hidden in the Fluid Dynamics section of the library.”

If you don’t understand the joke unfortunately, we really can’t explain it to you, but many fans saw the humour in it and couldn’t believe they never spotted it.

The joke is a bit hard to make PG in order to explain, think about it (Universal Pictures)

Others also took the chance to discuss the film more generally with one commenting: “I remember liking this when i was younger but rewatching as an adult after I'd lived through that time and could now relate to the characters i enjoyed it so much more.”

Another commented: “First few movies had the best sound tracks of all time. Still listen to alot of those bands.”

For those hoping that there will be another sequel, having already gotten American Pie 2, American Reunion, and American Wedding, one of the main parts of the film is up for it under the right circumstances.

Seann William Scott, who plays Stifler, said it would have to be the 'perfect idea'.

He said: "It would have to, you know? Because obviously so much has changed, comedies have changed. But I think the thing about that character too is that when it comes to comedies, that character allowed me to do so much. He could say so many things that were inappropriate but yet you still kind of loved him.”

American Pie airs tonight on Channel 4 at 10.35pm.