You’ve heard of ‘easter eggs’ in films.

They’re the hidden clues and references that give diehard fans of film franchises the chance to identify them and then talk endlessly about them on message boards and Twitter threads.

What you might not know is that easter eggs aren’t new. They’ve been around for centuries and some of the history’s most renowned artists included them, often, in their paintings.

Business Insider took a look at some of the world’s most famous paintings to uncover the hidden gems within.

‘Madonna with Saint Giovannino’ by Domenico Ghirlandaio

This painting has found itself at the centre of a range of UFO conspiracy theories.

Yes, that blurry circle next to the Madonna’s head has been at the center of a controversy for years. Many UFO conspiracy theorists are convinced that it’s a depiction of an alien aircraft.

People see what they want to see.

A section of the ceiling of the Sistine Chapel, called ‘Creation of Adam’, by Michelangelo

The shape of the cloak around God looks a lot like a human brain (or maybe a human heart?).

Vincent Van Gogh’s ‘Café Terrace at Night’

The folks gathered in the background look a lot like those gathered in Da Vinci’s ‘The Last Supper’.

Some believe that Vincent Van Gogh, an icon in his own right, paid homage to Da Vinci in his painting “Café Terrace at Night.” Specifically, there are 12 patrons at the café (like the Apostles), and the server in the middle definitely has a Jesus-like look to him.

You can also make out a crucifix shape in the window behind the ‘Jesus’ character.

‘Netherlandish Proverbs’ by Pieter Brugel

What appears to be a busy street scene could actually reference a range of Dutch proverbs.

Clockwise starting from left: the Earth is upside-down (the whole world is upside-down), a man is running with his behind on fire (running like your butt’s on fire), a man is warming himself at a house fire (not caring who is hurt as long as it benefits you/roasting marshmallows at a house fire), the three figures in the back standing in a line (the blind leading the blind), a fish eating another fish (there’s always a bigger fish), a man is holding a globe (got the world in the palm of your hand), a man in armor holding a knife in his mouth (armed to the teeth), and a man is hitting his head against a brick wall (hitting your head against the wall).

That’s a lot to cram into one painting.

Leonardo Da Vinci’s ‘Mona Lisa’

Arguably one of the most famous paintings of all time, it’s no surprise that it might contain a few secrets.

Members of Italy’s National Committee for Cultural Heritage reported that – when viewed under a microscope – the letters LV are visible in one of her eyes, and there are other less-decipherable letters in there as well. Also visible is the number 72 on the arch in the background. Or they could potentially be L and 2. The painting is over 500 years old.

Do we know what LV means? Nope. As for 72…maybe Douglas Adams got it wrong, and this is actually the answer to life, the universe and everything.

‘Garden of Earthly Delights’ by Hieronymus Bosch

This extremely naughty artwork contains music.

This scene is taken from the right side of the painting, from the panel that represents Hell. In the top left corner, a person with music printed across their rear end is visible.

A university student named Amelia noticed this music, and took it upon herself to transcribe the music and record it.

You can listen to what Amelia describes as a “600-years-old butt song from hell”, HERE.

‘Young Woman Powdering Herself’ by Georges Seurat

As far as we know, famous pointillist Georges Seurat never painted himself – with the exception of this one self-portrait.

The subject of this painting is Seurat’s secret mistress Madeleine Knobloch. Seurat loved her so much that he originally inserted himself in the piece. The window with a vase of flowers was revealed to be concealing a mirror where the reflection of Seurat painting was visible.

When Seurat showed it to a friend, he said that the mirror image looked weird, so he covered it up.

You can read up on more ancient easter eggs, here.

[source:businessinsider]