Also, plenty of good, old-fashioned butt music.

Wait, what?

Look a little bit closer and it soon becomes very, very evident that Bosch is a major ass man. The painting is not only full of butts, but features plenty of people sticking things into said butts. Here's a damned soul who surrendered a perfect bull's eye in a hellish variant of darts:

Hieronymus Bosch "We call 'em 'Brown Eyes.'"

It's easy to think that's just one of the many punishments in the "hell" section of the artwork. After all, it's not like the Eden and heaven panels feature weird ass stuff. Oh, wait -- have some horticultural sodomy:

Hieronymus Bosch Roses are red, violets are blue, Bury both stems in number two

Impressive as that may seem, the most noteworthy of "The Garden"'s asses is a seemingly unassuming one that is apparently on the verge of getting rimmed by a weird, pink meat-demon:

Hieronymus Bosch This was the original ending for Amadeus before they ran over budget.

A modest level of magnification reveals a set of musical notes inscribed onto the dude's ass cheeks:

Hieronymus Bosch Look! It's the intergluteal clef.

And, because Bosch was very, very dedicated to his buttock-y cause, he also included ass musicians to play said ditty:

Hieronymus Bosch Using the shittiest instruments available.

Yes, Hieronymus Bosch saw fit to hide an Easter Egg of sheet music tattooed on a sinner's ass in his magnum opus, and yes, you can actually listen to it here, as directed by former monk Gregorio Paniagua.

Bosch's musical ass has received a recent, strange resurrection in the blogosphere, as a musically inclined blogger made her own version of the ditty. Several others followed suit, including an enterprising gentleman who turned it into a strangely haunting Gregorian ass chant.

Renaissance man and possible supervillain Leonardo da Vinci greatly disliked depicting himself in his art, even shunning the opportunity to draw himself with an enormous dong. There is only one verified da Vinci self-portrait: a 1512 chalk drawing that, according to legend, gives strength to those viewing it. During World War II, it was actually removed from its residence in Turin and locked away for fear that Hitler would get his grubby mitts on it and gain superpowers.

Leonardo da Vinci How do you make Nazis even more insufferable? Selfies.

Of course, it's possible da Vinci wasn't as opposed to self-portraits as we think. It could be that the reason his selfies are so hard to come across is because he kept hiding them in places where they'd take centuries to find.

Wait, what?

In 2009, the art world collectively lost its shit when a potential da Vinci self-portrait was discovered. It was hidden within one of his many scientific papers, a treatise on flight and general ornithology called "Codex on the Flight of Birds." The portrait was so cleverly hidden that it had gone unnoticed for 500 years, until an eagle-eyed Italian journalist spotted what appeared to be a nose hiding between lines of text.

Leonardo da Vinci Elsewhere in this article, three noses hide between the lines. Can you find them all?

After meticulously clearing away the writing from a facsimile they created for this specific purpose, a face was indeed found underneath. There was just one problem: This was the face of a young Leonardo, which had never been seen before. It wasn't until art historians were able to age the newly discovered illustration with forensic software that they were able to conclude this was indeed the legend himself.

via MIT Technology Review Also, this is almost certainly a horcrux.

The 17th-century Italian master Caravaggio was a super talented artist but a notoriously difficult and violent man with a rap sheet long enough that the NFL is still trying to sign him as a free agent. After just a few years of reveling in the glory of Rome's art circles, he had to flee a pope-induced death warrant due to a small matter of murdering a pimp over a woman by cutting off his balls. So Caravaggio fled to Malta, where he soon found himself in hot water again, and was convicted for causing grievous bodily harm to a knight, which is actually kind of impressive for a baroque painter dude.

Ottavio Leoni This man is why knights wore chain mail over their groins.

OK, so Caravaggio not only managed to piss off the freaking pope, he was also an irredeemable dick. So why is history still in single-name terms with him? Why didn't the pope lock his paintings in some vault and let the guy's name sink in the unsung pits of history? Because Caravaggio redeemed himself with a carefully constructed self-decapitation Easter Egg, that's why.

Wait, what?

Sometime before his death at just 38 (fever or "mysterious circumstances," depending on whom you believe), Caravaggio attempted to atone for his sins by producing one of his greatest masterpieces, "David with the Head of Goliath", as a gift to the Papal court.

Caravaggio Unlike some depictions of David, this one wore pants. See crotch guards, above.

However, the painting was meant to be more than just a cool piece of art. Caravaggio had carefully painted Goliath's head to look like the artist himself. The victorious David, on the other hand, is generally thought to be a younger representation of the artist. Very faintly inscribed down the middle of the blade is the abbreviation "H-AS OS," Latin for humilitas occidit superbiam: "Humility kills pride."

Caravaggio Though some say it stood for "hacked a scrotum off Steve."

In other words, Caravaggio had symbolically beheaded himself for the pope, and was now asking if maybe they were cool now, please? Ballsy as the move was, it worked: His Holiness thought this was pretty cool and would have totally pardoned Caravaggio had the artist not died in the meantime.

The catalog of Pieter Bruegel the Elder focuses primarily on old-timey landscapes deliciously littered with insane details, from people getting blowjobs from monsters to folks wiping their asses on doors. It's almost like the man knew the Internet would come along eventually and was determined to fit in when it did. Even his most normal-looking paintings are weird as shit once you zoom in on them. For instance, the Easter Egg in this picture ...

Pieter Breugel Yes, this is one of his more normal-looking paintings.

... is a very, very literal one. Also, running away with a knife sticking out of it, because cock-a-doodle doo, mother! Alien poop waffles!

Pieter Breugel We're guessing this protests abortion. Or Denny's.

However, when Master Bruegel was on point, his keen eye for the detail and absurd were a killer combination. Consider "Massacre of the Innocents", one of the rare moments when Bruegel took his crazy cap off so he could wax political. The painting was technically your run-in-the-mill biblical horror scene of Herod's soldiers murdering all the babies in Bethlehem ... until you start noticing the little details.

Pieter Breugel Like the doggy. Wait, two doggies. No -- four doggies!

For starters, that's not so much biblical-era Bethlehem as it is a wintery village from Bruegel's contemporary mid-16th century. The soldiers doing all the murdering are also clad in distinctive Germanic and Spanish uniforms and insignia of the era. You can even see the Hapsburg eagle. It turns out, Bruegel's liberal depiction of the scene was a protest of Spain's brutal occupation of the Low Countries under the Duke of Alva, who Bruegel included in the painting as well.

And yes, of course they're all killing babies, Herod-style. Restorations have revealed that the piles of booty captured by the soldier -- hens, cattle, jars -- have mysterious shadows underneath them, which are all actually infants being attacked by the soldiers. So while the version most people have seen looks like this:

Pieter Breugel ... with women weeping over pots, because they really like pots ...

... Bruegel's original looked like this:

Pieter Breugel But that one guy's wearing a Santa hat, so Merry Christmas!

The reason behind these terrifying baby-murder Easter Eggs is Holy Roman Emperor Rudolf II, who got his hands on the painting shortly after it was finished, and went: "Shit, that won't do," and had its more controversial parts (e.g. hordes of dead children) painted over.

As for why Rudolf II allowed those "shadows" that eventually revealed the dead infants linger in the painting, well ... we're guessing he didn't. They just kept reappearing every time someone painted over them, because there's no way a painting with this many dead babies in it isn't haunted.

One artist, Nelson Shanks, knew how the incident should be immortalized: With a Lewinsky reference in Clinton's official presidential portrait, hanging in the National Portrait Gallery.

Wait, what?

Shanks was actually in charge of painting the portrait, so it's not like he just snuck to the gallery to smear lipstick on its crotch or something. His reference to the Lewinsky scandal was far more subtle, and went unnoticed for years until the artist himself revealed the secret last March. Do you see that long shadow looming over the fireplace, a little left of Clinton?

Nelson Shanks Hint: It's the direction his slick willy is pointing.

That shadow was in the room when it was painted, and it's the shadow of a female mannequin in a blue dress, custom positioned to create an effect not unlike that of a certain 22-year-old intern standing off to the side while the president of the United States paused for a moment to perform pelvis-thrusting power poses. To add insult to injury, this very real shadow is also supposed to represent the metaphorical one Clinton's antics cast over his time in office.

Haraz N Ghanbari/AP "I thought that looked familiar!"

Now, Clinton actually posed for this painting, so if you're wondering how Shanks wasn't beaten to a pulp with a saxophone the second Clinton walked in and noticed the blue-dressed plastic lady, it's because he only kept the mannequin in position when Clinton was not present.

Then they inserted pictures of it just everywhere.

Wait, what?

Although we didn't figure out its exact cycle until 1705, people have been aware of the random bright lights that we'd later find out were all Halley's Comet for a long damn time. It has been recorded in art for at least the last 900 years, featured in everything from jewelry and book margins to stoner posters and, oh, several world-famous artworks.

Here's a particularly heavy metal illustration of the Great Comet of 1528, which is -- you guessed it -- Halley's. The image was included in a surgical textbook, in a chapter titled "Des Monstres Celestes," which roughly translates to "celestial monsters."

Ambroise Pare Or, even more roughly, to: "ALIENS."

And then there's the priceless Bayeux Tapestry, a 230-foot-long embroidered banner that documents the events leading to the Norman conquest of England in 1066. It's basically a medieval comic book starring former kings Harold, Edward, and historical badass William the Conqueror. One scene also features Halley's Comet (top center), which appeared a couple months after Harold's coronation. It was considered a portent of doom and in those days referred to as "the terror of kings." It didn't hurt the comet's reputation that shortly thereafter, William the Conqueror arrived and chokeslammed Harold's jabroni ass to oblivion.

via Wikimedia Well, it didn't portend William's doom ...

Perhaps most notably, the comet is featured in Giotto di Bondone's biblical masterpiece "Adoration of the Magi," part of a fresco completed in 1305. In it, Giotto cast Halley's Comet as the guiding star of Bethlehem, the ecclesiastical GPS that led the Magi to baby Jesus:

Giotto Still didn't stop them from arguing the whole time that it would have been quicker if the comet had just followed their route.

That's why the star is given something it doesn't have in the story itself -- a tail, looking like it's streaking across the sky. You know, like a comet. That's because the painting was done in 1305, and Halley's Comet had swept by and created its usual sensation just four years earlier. So, the artist retconned it into a painting of Baby Jesus, as God's sign from the heavens. That's how big of a deal Halley's Comet was.

Jacopo della Quercia is the author of The Great Abraham Lincoln Pocket Watch Conspiracy and its follow-up License to Quill, both of which you should totally order now!

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For more things that aren't new, check out 24 REAL R-Rated Easter Eggs Hidden In Famous Pop Culture and The 40 Most Insane Easter Eggs Ever Found.