The level you're talking about for SMB3 is 6-5, not 6-6.
"The Top 10 Best-Kept Secrets of NES Games" Rewind a few years. It's 1992 and you're sitting in your living room, playing your favorite NES games. You've beaten them all dozens of times. You know 'em inside and out. You're a pro, and you enjoy showing off your skills to your amazed friends. Yet, in spite of your guru-level knowledge of the game, there's always this strange, random element with one part of the game that you can't quite put your finger on. Why did an item appear THERE that one time? What's this undocumented featre you somehow activated? How did you stumble upon this secret enemy you've never seen before? How did you bring up a secret save menu? More importantly, how do you do it again?? It bugged the heck out of you, and try as you might, you had no earthly idea what the game was doing behind the scenes. And you never would have, either, if it wasn't for friends, strategy guides, and GameFAQs to finally lay all the mysteries to rest. Some of them are so secret and obscure, I bet there will even be a few things on this list you didn't know yet! So here they are, the top 10 best-kept secrets of famous NES games you never would have figured out on your own. 10) Secret Player 2 Input (Mega Man 3) It's surprising how many games of this NES era had secret features unlocked by hitting button combinations of Player 2's controller -- almost as surprising as how long it took for you to realize they existed! They'd give you save screens without having to kill yourself, reset the game, even let you continue after a game over. But the most iconic and ridiculous of these had to have been Mega Man 3's debug features. Remember that day your little brother was randomly mashing buttons on Player 2's controller, and you found that Mega Man could suddenly jump SKY HIGH? And he could walk over pits without dying? Yeah, what the heck?! Well, now you know: hold Right on the other control pad to make Mega Man moonjump. 6) Not-Quite-Random Items (Bubble Bobble) The powerups in Bubble Bobble are probably the part of the game everyone remembers with the most fondness. They had all sorts of awesome effects, ranging from invulnerability, to super speed, to the ability to shoot bubbles as fast as a machine gun, to summoning a giant lightning bolt and killing all the monsters on the screen! When you saw that rare item appear across the map from you, you know you wouldn't think twice about making a reckless bee-line for it. But why did some items always seem to appear on the same levels every time, almost to the point where you could count on them? Weren't they supposed to be random? Not when YOU played, it seemed. And why did they always get mixed up when you were playing with a friend, or when you weren't quite playing your best? Well, the answer is simple: the items which appear in Bubble Bobble are based on your performance. Specifically, the game counts various things that you do, such as popping bubbles or jumping on bubbles, and when you accumulate a high enough count, a specific item will appear on the next round. Want that candy early? Pop lots of bubbles. Want the shoes? Jump on lots of bubbles. Want that rare, coveted green bonus potion? Fall off the bottom of the screen a lot! To make matters more confusing, those who had played the arcade version of the game long enough to pick up on this trick assumed their knowledge would carry over to the NES port, when all of these values were actually scrambled up to give totally different items. Either way, this mechanic was a brilliantly subtle way to reward everyone's own personal playing style. 2) The Case of the Disappearing 1-Up Mushrooms (Super Mario Bros.) Have you ever been just playing through the first Super Mario Bros., only to get to 2-1 and find that the invisible 1-Up mushroom wasn't there? Ever have this nagging feeling in the back of your head that they only disappear if you've been playing less than your best? This one bugged the heck out of me for all of my life, and recently I was told the answer. If you didn't know this already, you're never going to believe it: on the first stage of every world (1-1, 2-1, 3-1, and so on), there is an invisible block with a 1-Up mushroom somewhere on the map. These blocks will only appear if you collected every coin on the third stage of the previous world! So, if you want the 1-Up on stage 3-1 for example, you need to collect all the coins on stage 2-3. 1-3 is special in that you are allowed to miss 2 coins and have the 1-Up appear, and using a warp zone will cause the 1-Up to appear regardless on whatever stage you warped to. With such a secret, arbitrary, and not-widely-known game mechanic, Super Mario Bros. is still impressing us over two decades since its release. 1) Bald Bull's Photo Op (Mike Tyson's Punch-Out!!) This one was so secret, only acknowledged in the subconscious minds of the most avid players, that the developers recently had to let the secret out once and for all. When fighting Bald Bull, an audience member in the top-right corner of the screen will flash their camera at the moment the Bull Charge can be countered.
"The Top 10 Most Evil Levels in NES Games" THAT ONE LEVEL. That level you could never beat as a kid. You feared it. You dreaded it. You'd stock up on lives, dedicating hour after waking hour just to play through the game and try that level again, only to be reduced to tears every time. And when you finally got past it? You treasured that passcode like a newborn son. Only... it wasn't because the level was hard. Oh, no, the game was hard already. This level can only be described as EVIL. These are the levels that come after the game has lulled you into the complacency of a fun and addicting challenge, only to throw something NEW at you. Something DIFFERENT. Something DIABOLICAL. Something all of your skills would be useless against. These are the levels that had you stumped and overwhelmed. These are the levels that you wished didn't even exist. These are the levels of EVIL. 10) Super Mario Bros.: World 7-4 Proud of all the platforming skill you've gained just getting this far? They're all totally useless here. This is the level that repeats infinitely until you find the right route... or until time runs out. Usually the latter. I cannot begin to describe the frustration of trying to beat this level for the first time without using a guide, watching life after stockpiled life die from TIME UP. And it wouldn't actually be all that bad, except for the section in the second looping part where all the ledges are split up in pieces. What, are you supposed to try every combination of weaving in and out, over and under the ledges? The solution is deceptively simple once you know it, but pretend for a moment you're playing this back in 1993 with no internet and no guide. What's a self-respecting plumber to do? 9) Bubble Bobble: Level 57 If you've ever tried to play through the NES Bubble Bobble, you probably don't even have to look this one up. You know precisely which one I mean. The pink level of doom, where the space-invader enemies are trapped on platforms near the ceiling, constantly shooting laser beams down at you. Well, that's easy, just use bubbles and jump up to them, right? It's not that simple, because in this level, the bubbles float DOWN. The only way to win is to stand in the line of fire, blow a tower of bubbles in the center of the room, then jump on them before they straighten out fully and hope they don't just randomly burst when you land on them. No, it wasn't fun. It was a pure headache, and it took dozens and dozens and dozens of tries. But remember the joy you felt at finally obtaining the password for Level 58, vowing never to play that abomination of a level again. 8) Super Mario Bros. 3: World 6-5 That mushroom house inside the square taunts you. And it has a right to; there's a Hammer Bros. suit in there, the rarest and most awesome item in the game. But in order to get it, you have to go through the optional, fiendishly diabolical level 6-6. Prepare to be baffled! The exit to this world isn't anywhere obvious; if you keep going forward, you'll end up in an infinite loop until time runs out. The real exit is somewhere you'd literally never look: up in one of the several gaps in the ceiling. This means you have to fly, but the ground is uneven and covered with enemies and obstacles which keep respawning, including those blasted Buster Beetles that throw bricks at you that are somehow difficult to dodge. Get hit once, and you have to loop through the whole level over again to get your raccoon suit back. And when you FINALLY manage to clear the road and gather enough running speed to fly, and you manage to aim for the correct hole in the ceiling, you find, to your horror... NO! No, it CAN'T be! That's... that's just too evil! The exit pipe is blocked by some Nippers and you have to carry a koopa shell up with you to clear them out! UGH! Needless to say, after a dozen lost lives, almost all of which were from TIME UP, you truly earned that toad house. Unless, of course, you had a spare cloud in your inventory. Or a P-Wing... 7) Mega Man: Wily's Fortress 1 The Yellow Devil. Enough said. This boss is so infamous, it's a universally accepted technique to use a weapon glitch to beat him. But, again, think back to when you didn't even know about the internet, and there was nobody to tell you "just use the select trick!" You'd think, after all the hell you've braved, all those patterns of disappearing tiles and those impossible jumps and the infinitely spawning enemies that dive-bomb you from the side of the screen, you'd be ready for this guy. Right? Right? But no, you find that the the Yellow Devil is yellow from the sweat and tears of all the poor children who thought likewise. And there's no password feature, so if you get fed up and turn the game off, you have to play the whole thing over again. Even compared to the rest of the tough-as-nails game, this boss requires such reflex and precision that he's guaranteed to just mow over anybody on their first try. Or their second try. Or tenth... 6. Battletoads: Level 3: Turbo Tunnel