For as long as there have been video games, people have been hiding secrets in them. Sometimes they're meant to be found (like Easter eggs or hidden side quests), but other times not so much (such as backdoors left by the programmers). Some secrets aren't even really that secret since it seems like everyone knows them. For example, you probably already know that in Zelda II: The Adventure of Link, you can bypass locked doors with the Fairy spell. Or in Kid Icarus, most people already know that entering the code ICARUS FIGHTS MEDUSA ANGELS gives you unlimited lives. Or in Donkey Kong Country, you can start off with 50 lives by proceeding like you're going to erase a game, but then entering the code BARRAL (I see what you did there, Rare).

And that, of course, touches on a sticky aspect of these secrets: a lot of the time, they're cheating. Should the pure gamer avoid these glitches and secret codes that offer an advantage? Not necessarily. As I said, not all secrets are cheats; often they bring you to even harder challenges than can be found in the regular game. Also finding the secrets is almost always a challenge in and of itself, so how can it be cheating if you had to work so hard for it? Rules are made to be broken, and secrets are made to be found. So without further ado, here are 25 secrets from classic games that you STILL haven't found.

25 Gaming The Glitch

Sitting at #26 on the Guinness World Record's "Top 50 Games of All Time," Pokemon Red and Blue were staples of every kid who owned a GameBoy. With diligence, you might've been successful enough to catch all 150 Pokemon, but did you know there's a secret 151st Pokemon?

You can catch Mew by exploiting a glitch. Start over if you've played past Cerulean City. Once there, go North on Nugget Bridge, but leave the Jr. Trainer standing left on the grass. Capture the wild Abra, and return to the Jr. Trainer, but just as he sees you, press start and use your Abra to teleport. Next, proceed to the Youngster on Route #25 but don't engage him. Stand well above him until he approaches you. Defeat the Youngster's Slowpoke and return to Route #24. Your Start menu will randomly appear; dismiss it with B, and you'll find yourself battling Mew!

24 Just One More Thing...

If you're old enough to remember when Nintendo 64 launched in 1996 with Super Mario 64, It. Was. Mind-blowing. To switch from a lifetime of side-scrollers to a 3D open-world playground was like seeing color for the first time. The possibilities were endless. Per usual, Mario needed to rescue Peach from Bowser, but this time he had to navigate not only enemies in the new open world, but also varying missions, puzzles, and races, all while collecting stars.

After you've collected all 120 stars and defeated the third Bowser, you probably think you've beaten the game, but there's one more thing left to do. Head straight out of the castle to the cannon by the water. Jump into the cannon and shoot yourself to the roof. There you'll find Yoshi, who rewards you with 100 lives.

23 It's A Marathon, Not A Sprint

Getting Biggoron's Sword in The Legend of Zelda: Ocarina of Time is a CHORE, so let's jump right in. To start: grow up, rescue Epona, get the Fairy Bow, unfreeze King Zora. Then talk to the Cucco lady at Kakariko Village. Hatch the egg and use the Cucco to wake Talon. Return it to Cucco lady. Head to the Lost Woods; show your blue Cucco to the sitting guy. Race Epona to Kakariko within the time limit. Give the Weird Mushroom to the Secret Potion Shop lady. Back to the Lost Woods; give the Potion to the girl. Still with me? Then to Gerudo Valley; give the Poacher's Saw to the Craftsman, get Broken Biggoron's Sword. Go to the top of Death Mountain to find Biggoron. He sends you to King Zora. Quick to the laboratory at Lake Hylia. Trade frog for eyedrops, then race to Biggoron. Warp time forward to FINALLY get Biggoron's Sword!

22 Navy Seals?

Tom Clancy's Splinter Cell: Double Agent was a multi-platform release in 2006. The game features Clancy's character Sam Fisher, a black-ops NSA agent, as he attempts to infiltrate a terrorist group. You can play single-player or co-op, and certain levels and features are slightly different when playing on different platforms, which might explain how this whopper of a secret stayed hidden for so long.

In 2010, a bizarre side quest was finally uncovered in co-op mode on the Xbox version of the game. If players can find a gold piece in a locker, they can insert it into a vending machine to free a talking seal named Muffin. Muffin sends you on various quests to rescue her friends Cookie, Buddy, Pepperoni, and Vanilla. It's hard to maintain that tough-guy image when you're fetching snacks for a birthday hat-wearing baby seal.

21 Ready, Aim, Fire!

Along with Super Mario 64, Pilotwings 64 launched with the Nintendo 64 in 1996 (if you happened to live in Japan or Europe at the time, you could also get a third launch title, Saikyō Habu Shōgi). The game put the N64's new 3D technology to full advantage in this flight simulator game as players attempted to complete various types of missions in order to earn their pilot's license. Plus it included a super cool Easter egg.

In the Midwest of the Little States, locate Mount Rushmore (remember your geography?). You'll notice something a little strange, however: Mario's face replaces George Washington's. And since you've got a cannon, why not fire it at Mario? If you do, Mario's face transforms into Wario. You can change the faces back and forth at will, but each change requires an increasing number of shots.

20 Why The Mona Lisa Smiles

Released in North America in 1990, Super Mario Bros. 3 is the third best-selling NES game ever (behind the original Super Mario Bros. and Duck Hunt). Despite being called "the Mona Lisa of video games," Super Mario Bros. 3 did get one thumbs-down from critics, however: it lacked the ability to let players save their game. If only we'd all known this little secret back in the '90s.

If you run out of lives Super Mario Bros. 3, you don't have to start completely over from the beginning. Hold down A from the Game Over screen. Keep holding A as you return to the title screen and press start. You'll return to the first level of whatever world you were in when you died!

19 An Attitude Adjustment

In 2001, Wave Race: Blue Storm was released for GameCube as a follow up to the series' previous titles on Game Boy and N64. In the jet ski racing game, players maneuver around courses, objects, and the weather, to win against the computer or up to three other players, and the game is well-known for its superb weather graphics.

But after a while, regular jet ski racing can get a little boring. Fortunately, there's a secret to help you liven things up a little, and it wasn't even discovered until eight years later. From the Options menu, go to Audio Settings. Tap Z repeatedly until the waveform looks like fog. Then enter code UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, A, X, Z. You'll get a confirmation and, from that point forward, an announcer with a snarky new attitude.

18 The Truth Is Out There

The third installment in the Hitman series, Hitman: Contracts, was released for Xbox, PlayStation 2, and PC, in 2004. In this stealth game, players guide Agent 47 through various levels and missions as he attempts to bring down a child slavery ring. The gameplay is flexible, and players can proceed through missions more or less however they choose: with a run-and-gun style or a more subtle approach.

There is something a little ghostly in the Thermal Bath Hotel, however. If you go down the hallway to the right on the ground floor, you'll come across a closed area (which, of course, means you should go inside). As you explore the rooms, peek in the mirrors if you dare; it turns out the rooms aren't unoccupied after all.

17 Save More Than The Princess

Since its release in 1986, The Legend of Zelda has been one of the most successful video game franchises of all time (rivaling both Final Fantasy and anything else Nintendo has ever come up with). Players guide our hero Link around the kingdom of Hyrule, helping him to rescue Princess Zelda. The original Legend of Zelda takes around 9 hours to beat, which is an eternity in NES time. Fortunately, the game does let you save, but only when you die. Assuming you prefer living over dying, however, you're probably interested in an alternative method of saving your game.

Wish granted. First, you need two controllers. Whenever you want to save, hold start on the first controller, then press up and A on the second controller. Magical secret save time!

16 A Race Against The Clock

If you've ever wished you could defeat evil space pigs with your killer kart racing skills, Diddy Kong Racing is your game. Released in 1997 for Nintendo 64, the game lets players choose between several characters and types of vehicles, as well as a handful of different race modes. Progress through Adventure Mode successfully to race the boss WizPig; win and you unlock Drumstick as a playable character. But did you know there's one more character you can unlock?

In the game, TT is an anthropomorphic clock who saves your best lap times. Once you find all the Challenge Keys, you'll have the option of racing TT in Time Trial mode. It'll take lots of practice, but if you beat TT's time on all 20 tracks, you unlock him as a playable character.

15 For RPG Overachievers

Arguably the greatest title in the Final Fantasy series, Final Fantasy VII was released on PlayStation in 1997. The JRPG follows primary protagonist Cloud Strife and company as they attempt to save the world from an evil super-corporation and a psychopath with mommy issues. The game features Final Fantasy's traditional turn-based gameplay, a killer soundtrack, and a storyline with a seriously epic twist.

If saving the world isn't enough for you, there are two additional bosses in the game to provide an extra challenge. After you defeat Ultimate W.E.A.P.O.N. (the last of Gaia's five creations), you can find Ruby W.E.A.P.O.N. in the sands of the Gold Saucer desert. Emerald W.E.A.P.O.N. can be found in the inland sea once you have the Shinra Sub. If you pick these fights, then be careful what you wish for; both bosses are strong enough to kill you in a single attack if you're not prepared.

14 For A Good Time Call

The critically acclaimed God of War series is issuing its highly anticipated eighth installment (God of War 4) next year. First released in 2005 for PlayStation 2, the original is a hack-and-slash third-person combat game based on Greek mythology. Players control Kratos, a Spartan who has sold his soul to Ares, God of War, as he fights for freedom from the bondage of the gods.

If you thought they didn't have phones in ancient Greece, well, you'd be wrong. Upon beating the game in God Mode, players are given the phone number 1-800-613-8840; call it to receive a congratulatory voice message from Kratos. If you destroy the two statues in Kratos Throne Room, you receive the number 1-888-447-5594; call it to listen to a message from creator David Jaffe and Kratos. Best of all, I verified for myself as I wrote this: both numbers still work after 12 years!

13 The Poster And The Creep

Released in 2001 for PlayStation 2, Metal Gear Solid 2: Sons of Liberty is the fourth installment of the Metal Gear series (that made a legend out of creator Hideo Kojima). In this stealth game, players control a rookie agent named Raiden as he works to take down the Sons of Liberty, a terrorist organization. Rather than being just another dumb action game, the plot of MGS2 involves themes of memetics, existentialism, and post-modernism.

It's not all brains over brawn, however. MGS2 is packed full of Easter eggs, and a lot of them are decidedly non-G-rated (for example, Kissing Booth and Snake Beater are just two trophies you can earn). To see what I mean, when you open a locker with a poster of a model inside during the game's prologue, call Otacon and watch what happens.

12 A Whole New World

Released for NES in 1985, the original Super Mario Bros. is the one that started it all. Credited with reviving the video game industry after it crashed in 1983, Super Mario Bros. popularized the side-scrolling platform genre that dominated game design until the advent of 3D.

One of the things that makes the game so great is that it's full of secrets, and since it's been around for over 30 years, most of them are extremely well known. But here's one you might not know: at the end of level 1-2, stand on top of the green pipe rather than going inside. Break the blocks above you, but leave the right-most one. While facing left, jump up and right. If you do it correctly, Mario passes through the wall into a Warp Zone. The first pipe takes you to World -1, a never-ending water level.

11 The End Of The End

Released in 2004 for PlayStation 2, Metal Gear 3: Snake Eater is the fifth Kojima installment and serves as a prequel to the first Metal Gear. Set in a Cold War-era jungle, players control Naked Snake, an operative attempting to rescue a rocket scientist. Despite its departure from the series' normal setting and time period, the game was a huge success, even being named to Popular Mechanics' "The 100 Greatest Video Games of All Time."

One of the toughest bosses in MG3 is The End, a legendary sniper over 100 years old. Beating him requires a complicated cat-and-mouse game where simple mistakes such as leaving footprints or using your binoculars too much will give you away. Looking for an easier method? Once you begin your showdown with The End, simply wait one week (or set your PS2's clock ahead a week), and The End will die of old age.

10 You're Gonna Need A Bigger Boat

When Resident Evil 4 came out in 2005 as a multi-platform release, I spent three days straight parked in front of my GameCube, barely eating or sleeping until I'd beaten the game. And considering that RE4 received not one, but several, Game of the Year awards, I'm clearly not the only one who felt this way.

RE4 follows special agent Leon S. Kennedy (back from RE2) as he attempts to rescue the president's daughter from a cult in rural Spain. Having escaped from the first zombie village and the terrifying Chainsaw Ganado, Leon comes to a lake. If he crosses, he'll battle the fearsome Del Lago, a mutant lake monster. But what if he doesn't cross? What if he just shoots the lake a bunch of times? Try it, and Del Lago will swallow Leon whole. But hey, at least you got the "Don't Shoot the Lake" trophy!

9 It's A Trap

Ah, the dungeon quest, that time-honored video game trope for turning players into heroes. Released in 1999 for PC, Dungeon Keeper 2 flips this role on its head. In this strategy game, players must build and defend an underground dungeon from invading heroes. And if you're looking for a little advantage in your mission, I have some secrets that might interest you.

Press CTRL + ALT + C, and you'll hear the sound of a door opening. Now you can enter any number of codes to unlock in-game cheats (for example, type "show me the money" to get a money bonus). Hold the left shift button and type SKEKSIS to hear messages from the programmers until you release the left shift. Set the clock to 2:50 a.m. and when it hits 3:00, you'll get the message, "Your nocturnal perseverance has your earned you a secret: GO TO BED!"

8 The Hug Life

The first-person-shooter Halo franchise is single-handedly responsible for forcing thousands of PlayStation die-hards to finally buy an Xbox. The games are just that good. Released in 2001 as a launch title for the Xbox, Halo: Combat Evolved tells the story of the Master Chief, a cybernetic-enhanced super soldier, as he battles the Covenant, an alien race seeking to learn the location of Earth. The game was a massive success, earning a score of 97/100 on Metacritic and spawning an iconic franchise.

It's not all macho gunfire and explosions, however. Sometimes you just need to hug things out. To see what I mean, first beat The Maw on Legendary difficulty. Then enjoy the non-canon cutscene showing a battle between Stealth Sangheili and Sergeant Johnson that takes a touching turn.

7 Cutscene Chaos

Based on the James Bond film GoldenEye, 1997's GoldenEye 007 was a forerunner of many aspects of FPS games that we now take for granted (single-player missions vs multiplayer deathmatches, stealth, and strategy, etc.), and this helped propel it to the third best-selling N64 game of all time.

In the game, players control Bond as he tries to stop the GoldenEye, a satellite EMP weapon. Naturally, the game uses a lot of cutscenes. Do you hate cutscenes? Me too. But in GoldenEye 007, there's a way to improve them. First, you'll need two controllers. Next select layout 2.3 or 2.4 from your watch menu (this changes the fire button to the second controller). Just before finishing a level, hold down the fire button until the weapon dry clicks. End the level to trigger a cutscene, and when you release the fire button, the weapon will shoot one last bullet.

6 7777 Is A Lucky Number

As I mentioned earlier in #15, Final Fantasy VII contains two super bosses that will be of interest to completionists. But be forewarned: if you go unprepared, you will die. Quickly. Ruby W.E.A.P.O.N. has 800,000 hp and is immune to most status effects while Emerald W.E.A.P.O.N. has 1,000,000 hp and is likewise immune to most status effects. For comparison, Safer-Sephiroth (Sephiroth's final form and the game's final boss) only has 80,000-400,000 hp (depending on a number of factors). So if you're going up against the super bosses, you need all the help you can get.

One helpful trick (though a difficult one to pull off) is to take advantage of Lucky Sevens Mode, which occurs when one of your characters' hp is a number containing all 7s. During this time, your character can deal 7777 worth of damage.