Secret levels and Easter eggs are now an accepted facet of gamer culture. As soon as we pop a new disc into our consoles or start up a game we just downloaded, we already assume that developers have hidden goodies for us to find. It's no longer a question of if there will be a secret; it's where the secret will be located. A desire that a lot of gamers share is a passion for working out the riddles of a game. There is nothing more satisfying than discovering a secret level that has been expertly hidden. You feel as if you are the king of the world and that all should bow before your brilliance. Of course, there is also nothing quite as hilarious as accidentally stumbling onto a secret level and being thrust into an absurd and confusing situation that you can't seem to get out of. Either way, secret levels mean you are in for a fantastic time.

With the advent of the Internet, it's easier to uncover Easter eggs than before. Just using a search engine could help you find millions of entries that exist solely to help you solve those puzzles and access those cheat codes. Whether that cheapens the experience of finding the secret or not is entirely subjective. But the fact of the matter is, if someone has discovered the location of a secret level, odds are his or her findings will be posted somewhere. That wasn't always the case. Back in the olden days, intrepid gamers had to thoroughly examine every inch of their games on their own.

We've gathered together a list of 20 secret levels from several games that you might have missed or never found yourself. No matter how old the game is, a secret is a secret, and we included it on our list.

20 It's-a Me! Zombie Mario!

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Zombie survival games make for popular games, and Dying Light is no exception. This open world, first-person survival game contained great graphics, a dynamic day-night cycle, and excellent combat. And if the story was a little on the boring side, the fun you had scaling rooftops and avoiding zombies more than compensated for the lackluster plot.

The gritty survival game took a turn for the lighthearted with its secret Mario level. If you're running along the rooftops of Old Town, there's a large brick building near the southern edge of the area. Inside one of this building's chimneys, a tiny green Mario pipe is nestled quite comfortably. Jump inside and you'll be transported to a rendering of a Mario level, complete with a zombie goomba.

19 My God, It's Full Of Stars

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Super Mario World is heralded as a superb entry in the excellent Mario series. It showcased its graphics on the Super Nintendo Entertainment System (SNES) and was welcomed for its simplicity while still remaining engaging. I don't know about you, but I could play Super Mario World for hours. It's like Mario invented replay value. It strides along that line between tough and easy so expertly that you can be challenged, but never frustrated.

While not exactly hidden, Star World had to be unlocked by completing tasks across various maps in order to reveal Star Roads. Each Star Road opened a level in Star World. There were five levels in Star World, and if you found the secret Star Road 6 in the fifth level, you unlocked 8 special levels.

For some shocking facts about Super Mario World, check out this list!

18 Mining In The Borderlands

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No one forgets their first time playing Borderlands. The humor, the unique art style, and the downright addictive cooperative play created an experience that is unforgettable. Borderlands 2 continued the tradition of a high-flying fun adventure that was partly a wacky Western, partly a science fiction romp, and partly a trip into insane good times. And with such a sense of humor, of course the developers would want to include a zany secret area.

If you head to the Caustic Caverns, the northwest corner of the area has two mine tracks with carts on them. If you follow the track on the right all the way to the end, you will find dirt blocks you can melee out of the way. After that, the path to the hidden Minecraft area is open. From there, you have the opportunity to collect a Minecraft skin and head. And you have the chance to meet a few Creepers. That too.

17 Adventure Is Out There

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When I first saw Adventure (made for the Atari around 1980), I thanked my lucky stars that I had been born in an era where my game protagonists were no longer little squares. But for its time, Adventure was a game that brought many concepts to the table that hadn't been there before. Most notably, its inclusion of an Easter egg made the idea of secrets in a video game widely popular.

Developers weren't given as much credit for their work as they are now. Warren Robinett, a developer of Adventure, wanted to correct this oversight. If a player collected a near-invisible dot as a key to open a wall near the Yellow Castle, they were treated to a small room with the developer's name displayed for the clever few who reached it.

16 Attack Of The Giant Ants

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The Command & Conquer series is an undeniable entry in the legacy of real-time strategy (RTS) games. The scope of its numerous games have earned it a spot in any RTS hall of fame. Deeply rooted in science fiction, the game has you pit factions against each other as they fight for control of Tiberium, a crystal that is simultaneously a valuable resource and a dangerous toxin for the planet.

For the most part, the Command & Conquer series has been layered with a seriousness that only the apocalypse and war could bring. In the Red Alert collection, things decidedly change from serious to comedic. In the Counterstrike expansion for the first Red Alert game, players could access a secret campaign called "It Came From Red Alert!" In this campaign, players learn that the Soviets have been replaced as opponents by these giant ants. You can then wage war against the ants as a faction in their own right.

15 Old-Time Nightmares

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Wolfenstein has a reputation to protect. This is not a reputation built on stodginess and prim manners. It is a reputation built on undermining Nazis and foiling their plots. While the first two games in the Wolfenstein series are good games, it was id Software's Wolfenstein 3D that popularized the franchise and the first-person genre. When MachineGames, developer of the 2014 Wolfenstein: The New Order, got a hold of the reins, they did not disappoint. Not only was the gameplay fast-paced and fun, they included a secret Easter egg where players could revisit the halls of Wolfenstein 3D.

In Chapter 5 of The New Order, if players guide their character to a poster of Wolfenstein 3D, they can enter the "Nightmare," and play the first level of Wolfenstein 3D, old school graphics and all. It's a touching tribute to id Software's revolutionary game. Yes, I'm using the word touching to refer to a game about this.

14 Egyptian Nightmares

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GoldenEye 007 is a pinnacle of achievement in terms of first-person shooters. It had immersive environments and a definite magnetism when it came to playing multiplayer with friends. It was also chock full of secrets that players could try to sniff out. The secret we are focusing on is the bonus level Egyptian. It was the last bonus level, and it could only be unlocked by completing every other mission on the hardest difficulty setting. If you managed to achieve that, besides being prouder than a guy who just beat Dark Souls, you had the chance to obtain the Golden Gun.

What's the Golden Gun, you might ask? Only a gun that can kill nearly all enemies with a single shot. In order to get it, you had to navigate Bond across a tiled room along a specific path. If you took a wrong step, indestructible guns would appear and whittle you to death unless you booked it out of there and started the whole puzzle again. Worth it? Well, once you're actually holding that shiny yellow gun, I'd say it was totally worth it.

13 The Painted World Of Pain

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I mentioned Dark Souls in that last entry as an example of a game you should be proud to beat. Dark Souls is infamous for its riveting boss battles and its insane level of difficulty. Passing the game is a feat to be immensely proud of. No amount of happiness can compare to a gamer's upon defeating a boss after the hundredth time fighting it, reducing its health bar millimeter by millimeter. So it only stands to reason that a secret level in a Dark Souls game would be tough to reach and tough to pass.

In order to get to this world, you must retrieve the Peculiar Doll that rests at the very beginning of the game, and then take it all they way back to Anor Londo, more than halfway through the game. Using the doll, you can go into a painting. This takes you to the Painted World of Ariamis. Once there, you can't get out easily. You have to go to the basement area, unlock the boss area, and then traverse the area between the basement and the boss area. There are enemies for you to fight the entire way, and any of them could swing the blow that ends you and sets you back to the bonfire. Once you reach the boss, Crossbreed Priscilla, you have the option to fight her. If you're like me, you left her well enough alone.

12 The Prince Of Secret Levels

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When you think of the Prince of Persia, it is my dear wish that you do not think of the Jake Gyllenhaal Prince of Persia first. Before it ever landed on the big screen, Prince of Persia was a video game. It was a solid action/adventure platformer. And when its successor, Prince of Persia: The Sands of Time, released to critical acclaim as well, the franchise was considered one of the greats.

From the main menu of the game, if you press certain keys on your controller (and the keys depend on which system you're using to play the game), you will unlock a Secret Level based off of the original Prince of Persia. Once you play and complete this hearkening to the older platformer, you will become the proud new owner of a brand spanking new sword. Or actually, since the Prince discovered it within all these caverns, it's probably an ancient sword.

11 And They Called It Seal Love

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Imagine a game where you have to rescue adorable baby seals who have found themselves trapped in various locations. Welcome to the secret co-op mission from Tom Clancy's Splinter Cell: Double Agent. With names like Muffin and Pepperoni, seals are scattered in various hidden locations, requiring you to find codes to safes and coins for vending machines in order to free them.

When you think of Tom Clancy's Splinter Cell, baby seals named Vanilla are not the first things that come to mind. Using your wits and reflexes, in Splinter Cell: Double Agent, you're supposed to remove enemies with extreme deliberation and complete objectives judiciously. Rescuing a couple of baby seals with a friend is a nice break from all that heavy stuff.

10 Smashing It Up In The Mushroom Kingdom

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Super Smash Bros. probably sounded ridiculous the first time the idea was pitched. Why would Pikachu fight Mario? What are Samus and Link even doing in the same universe? What is going on?! The result of this confusing mash-up was an all-out phenomenal fighting game where players could enact the unlikely scenario of Kirby and Donkey Kong getting into a scrap. As the years have passed, more and more characters have been added to the roster. With more characters come more arenas based off of the plentiful locations each fighter brings from their home game.

Mushroom Kingdom is the only unlockable stage in Super Smash Bros. In order to unlock it, you have to complete the 1-player mode with all eight of the beginning characters, and then you have to play on all of the arenas (with any character) in Versus mode at least once. The unlocked stage included a large gap smack dab in the middle for unwary players to fall in, some pipes, and multiple floating platforms.

9 Quaking In My Boots

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id Software is no stranger to secrets. I cannot recall a time when I did not know that. I remember walking around the imp-infested rooms of Doom and clicking each wall, searching for the secret compartment that I knew would be there. Quake was Doom's heir. Its fast-paced action and true 3D rendering made it an improvement on its predecessor. And it wouldn't be an id Software game if it didn't have secrets.

The best secret in Quake is the level Ziggurat Vertigo. In this hidden level, gravity is reduced, which dramatically alters the manner in which you play the game. You jump far higher than usual, and your falls are drawn-out affairs. As such, your speed and movement need to be taken into account when playing in this area. The breakneck pace with which you used to approach combat does not work the same way, especially as pools of lava are scattered throughout the map. I zoomed my way to a fiery death more times than I can count. But Ziggurat Vertigo's departure from Quake's standard formula was exhilarating and rewarding once you got the hang of it.

8 Do You Even Tofu, Bruh?

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This is no joke. It's funny, but it's no joke. You can play as a slab of Tofu in Resident Evil 2. Tofu is a secret character you can unlock after unlocking and completing another mini-game within Resident Evil 2 called The 4th Survivor. If you finish The 4th Survivor, and end the main storylines (Leon A/Claire B) with an A rating three times, you unlock the Tofu mini-game.

The piece of Tofu you play as goes through the same area that the main character of The 4th Survivor does. The only difference is that... well, he's a piece of tofu! How awesome is that? His only weapon is a knife, but he can take a hit better than a human. I'll bet that if you haven't played Resident Evil 2 yet, you're dying to now.

7 The Empire's New Hope

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Rogue Squadron is one of the best series to demonstrate the entertainment of simulating flying in a spaceship. When you played these games, you felt as if you were actually in the cockpit of an X-wing fighter. Say what you will about the graphics, the experience is undeniable, especially to a little kid who grew up adoring the Star Wars franchise. In Rogue Squadron II: Rogue Leader, players were placed in the ships of Luke Skywalker and Wedge Antilles, two of the heroes of the Rebellion.

However, in a secret level called Triumph of the Empire, you take on the role of Darth Vader at the Battle of Yavin, soaring over the Death Star in your TIE fighter. In this version of how Star Wars could have ended, you can destroy Biggs, Wedge, and Luke, and destroy the Rebel Alliance in one swift stroke. Talk about changing history.

6 The Villainous Slot Machine

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Star Fox was a fun vehicular romp. The Arwing should be on any list of top spacecraft in video games. We learned what a barrel roll was from this game. We would shoot and roll, roll and shoot. The villains were a tad cartoon-ish, but that only added to the appeal. Come on, we were playing as an anthropomorphic fox. It only makes sense that the villains we would face would be equally zany.

One "villain" takes the cake. If you shoot a certain asteroid while flying in the asteroid belt of level 3, a giant bird appears out of nowhere and when you fly straight to its breast, you are suddenly transported to "Out of this Dimension," a secret level that you can't escape from unless you shut down the game, not even if you defeat the boss. Oh, and that boss is a giant slot machine that waves in and out of existence.

5 The Secret Reptile

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Since the first Mortal Kombat, the developers have included what are known as secret characters, characters hidden away that require some finagling to locate and then fight. Reptile was the first secret character in the Mortal Kombat series. In order to find him, you had to go to the Pit fighting area, perform a Double Flawless Victory without blocking (at all), and then execute a Fatality.

Once this was done, you were able to fight him below the Pit. At the time, he just looked like a green Sub-Zero, but he actually possessed the moves of both Sub-Zero and Scorpion. His speed was also quadruple your own, so beating him was one tough cookie.

4 Just A Sprinkling Of Doom

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As you might have noticed, id Software and their successors have appeared on this list a few times. Wolfenstein, Quake, and now Doom all keep up with the legacy of secrets that id promulgated. Doom (2016) was a perfect blend of old and new that made for an extremely satisfying campaign. The speed of the original Doom was back, and the weapons upgrading system was never annoying (at least not to me). And of course, it wouldn't be a re-imagining of an id Software game without a few secrets.

Scattered on each mission were multiple secret areas, and on each there was a classic Doom map. To find those maps, you first had to find levers that were hidden in hard-to-reach spots. When you pulled the lever, the trill of the original Doom's soundtrack played, and you then had to search for where a wall had disappeared, revealing a beautifully recreated Doom area.

3  Slender: The Missing Ending

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Slender: The Arrival is a horrifying addition to the Slender Man library of games. It takes you through an empty house, which brings up all those bad memories of you being left home alone on a windy night, a classic Slender Man wooded area, and a jump-scare-filled mine. Upon finding out that the game contained a secret ending, we all hesitated before trying to find it. What if it led to something even creepier than the game itself?

To find the secret ending, you must approach and collect the missing poster of a child named Charles Matheson Jr. Be warned! If you achieve this secret ending, exiting it will not be so simple. Without spoiling what happens, I will say that, while not particularly revealing plot-wise, the secret ending does include quite a few scares.

2 Flip It And Reverse It

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When confronted with an enemy in a video game, normally, your first instinct is to destroy it. That's usually the main objective of any game: removing an antagonist. As such, making the decision to not obliterate your enemy as the deciding factor in revealing a secret area is a clever way to hide said area. This is the situation that you are faced with in Castlevania: Symphony of the Night.

If Alucard, the main character of Symphony of the Night, decides to free Richter Belmont from the spell an evil priest has laid upon him instead of eliminating him, an inverted version of Dracula's castle appears. The layout of this new castle is an inverted layout of the original castle. There are new enemies within, however, and new items for you to find.

1 Attack Of The Moo Moos

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Diablo II is an amazing sequel to its already amazing predecessor. Taking up the story shortly after the events of the first game, a new band of adventurers must stop the evil that was beginning to be released at the end of the first game. Hailed as an engrossing RPG, Diablo II deserves to be called a classic, if not for its gameplay then at least for the best secret level ever to be created.

Rumors of a secret cow level began with the first Diablo, but those rumors were unfounded. Obviously not wishing to disappoint fans, developers included a secret cow level in the second game. Thus, the Hell Bovines were created. After creating a portal, players can visit this most secret of cow levels, the diabolical Moo Moo Farm. This secret level comes with an assortment of normal cows and one Cow King.