It's actually a little unfair that Nintendo continues to be dismissed as a company that only makes games for kids and families. After all, this is the same company that published Conker's Bad Fur Day and Bayonetta 2 (among many other M-rated games), as well as allowing all Mortal Kombat games on Nintendo platforms to be unedited after the first one and also letting BMX XXX for GameCube include live-action footage of fully topless dancers.
But this list isn't about naughty content in Nintendo games that are specifically aimed at adults. Rather, the inappropriate content on this list was sneaked into Nintendo games that were specifically marketed as family-friendly, and weren't rated anything higher than T for Teen (or its equivalent in other regions). Furthermore, we only considered games that are actual Nintendo games, not just games that have appeared on Nintendo platforms.
20 Bowser's Baby Mama
How many giant female dinosaur/turtle/monster creatures have you seen in Mario games? Zero. Yet, somehow, Bowser was able to find a female to conceive a child with. Who could Bowser Jr.'s mother possibly be? Well, we know which woman Bowser has spent a lot of time with. Too much of a stretch for you? How about the fact that Bowser Jr. calls Peach "mama" in Super Mario Sunshine, and she doesn't try all that hard to correct him...
19 Hyrule's Oldest Profession
The media went nuts over the fact that Grand Theft Auto III allowed players to replenish their health by getting intimate in taxis with ladies of the night. Never mind the fact that Link refilled his health meter in a similar fashion in Zelda II, being invited into the homes of the red dress-wearing ladies of the villages and having his hearts magically replenish after he disappears behind their door. We see what Link is doing inside the other houses in the game, so why not those? Hmm.
18 What Goes In, Must Come Out
Kirby is one of those characters that its best not to think too deeply about. After all, his primary mechanic is that he inhales other characters and then swallows them to steal their power. As gross as it is to imagine what the inside of Kirby's belly looks like, it's even more disturbing when you think about what Kirby is likely doing when he ejects stars and other rejected items out behind him.
17 Samus The Snake Charmer
Anyone who was already familiar with the Metal Gear Solid series knew that protagonist Solid Snake had a tendency to flirt with and make suggestive comments about the various females he encountered. But his appearance in Super Smash Bros. Brawl was a lot of kids' introduction to him, so they might not have realized what he was getting at when he talked about "testing" the "skills" of Zero Suit Samus.
16 Candy Kong Offers Private Tutoring
Developer Rare was infamous for putting a lot of risque things into their games, and the many titles they created for Nintendo over the years were no exception. Even before they went all-out M-rated with Conker's Bad Fur Day, they sneaked plenty of lewd stuff into their supposedly kid-friendly games. But what's most surprising is how far Nintendo let them go with Donkey Kong 64, not only in terms of Candy Kong's curves and ill-fitting clothing, but in her offering to help DK with his "instrument."
15 Getting Steamy With Peach
The Paper Mario series is where Nintendo lets itself get a little looser, and there are things that are seen, said, and done, in a Paper Mario game that Nintendo would never allow in a mainline Super Mario title— such as this scene from The Thousand Year Door where we watch Princess Peach take a shower. Okay, so we don't actually see her in there, but the game makes a point to play the sound of her unzipping her dress and then shows her throwing her clothes up over the curtain, followed by steam billowing out from the shower. All this in a game for children.
14 Captain Creeper
Overall, the Animal Crossing series might be Nintendo's most wholesome franchise, from its gameplay mechanics to the general vibe of the universe. However, one glaring exception is the character of Kapp'n, who is just a fun-loving drinking buddy with the male villagers, but takes female villagers on boat rides where he sings songs to them full of cringey, uncomfortable come-ons. He's been toned down a bit in recent installments, but the damage has already been done.
13 Internal What Now?
High up on many gamers' wish lists for Nintendo franchises that need to come to Switch is Pikmin, a series of charming strategy games that started on GameCube. Overall, there isn't much inPikmin that our innocent young brains would've missed, except for Louie and his description of Pikmin 2's Waterwraith. The extremely suggestive blurb reads, "Known to cause mass hysteria, followed by leg spasms and internal thunderings." A description for the Big O that only Nintendo could come up with.
12 Krystal Needs Someone On Her Tail
People have long made the joke that the Star Fox series helped to awaken an entire generation of "furries," but there's no denying that many young gamers had confusing "feelings" about the character Krystal. To compound matters, the Star Fox series loved to play with the already naughty-sounding lingo of flight combat, making double entendres— much of it aimed directly at Krystal— about covering each other's tails and riding each other's wings.
11 Hyrule's Oldest Profession, Part 2
Hyrule seems like a much seedier place than we realized when we were kids. Not only did we completely miss what was probably going on between Link and those ladies-in-red in Zelda II, but this joke from Ocarina of Time's Poe Collector also completely went over our heads. The things people are willing to do for Rupees!
10 A Princess Never Tells
Super Mario RPG was an unusual game for Nintendo, as it was one of the first times the company let another developer come in and do their own take on the Mario universe. As such, there are a lot of elements in the game that you wouldn't find in your average Super Mario title, such as the ability to find a very personal item belonging to Princess Toadstool (Peach) that she kept near her bed and was very embarrassed to have someone find.
9 Sometimes You Feel Like A Nut
Before Fire Emblem and Xenosaga were Nintendo's main RPG series, they had the Golden Sun games for Game Boy Advance and DS that were beloved (and are now missed) by many Nintendo-loving JRPG fans. And like most Nintendo franchises, the games had their fair share of blink-and-you'll-miss-it dirty jokes, from the moment seen above— you can't even choose "no," by the way— to the original game crafting a very suggestive exchange between two characters upon the discovery of an item called the "Hard Nut."
8 That Level Layout Seems...Familiar
Sometimes, our minds turn something innocent into something dirty. Other times, something is exactly as inappropriate as it looks, as is the case with the above level layout taken from a section of the game Kirby's Dream Land 2. And maybe it's just us, but the fact that the lewd arrangement of blocks are topped off with a smiley face just makes the whole thing feel that much naughtier.
7 Professor Layton And The Red Light District
The puzzle series Professor Layton is one of Nintendo's more underappreciated franchises, and the games are a must for anyone who loves old-school adventure games like Myst and Broken Sword. It is also home to more than one inappropriate moment, including a heavily-inferred "red light district" complete with brothel in Professor Layton and the Diabolical Box, even informing the Professor's child partner that he is too young to go there.
6 We All Had A "Special Tape" Once...
Remember how we said that Nintendo gets a lot more risqué with the Paper Mario games than they normally would? That tradition started with the original installment for Nintendo 64, with the first example of it happening very early on in the game when a young Goomba is frantic over losing his "special tape" that he kept very well-hidden, and never divulges the contents of. And if you remember when such "special" content still came on tapes that people had to hide, you are officially old.
5 Peach Should Invest In Some Tights
We can't blame Nintendo that players took the opportunity to zoom and pan the camera to look up Peach's dress in the Super Smash Bros. games. However, there is a difference between having Peach's undergarments be a basic pink covering, and having extra detail put into the frills of her panties and to have them hug her behind just so as it did in Super Smash Bros. Brawl. That was clearly a "reward" meant for older Smash players only.
4 Flirty Fairies
Game developers could get away with a lot more back when graphics were much more primitive and basic. We probably didn't notice the fact that Ocarina of Time's Great Fairies were basically naked except for strategically-placed vines— and that they were especially voluptuous— given the limits of the Nintendo 64 hardware. But when those same character models were given a more realistic upgrade in Hyrule Warriors, it became clear just how naughty the design of the Great Fairies actually is.
3 Puppy Love
We know what you're thinking: How can a game about taking care of cute, cuddly puppies and kitties possibly have any underlying inappropriateness? Well, what you probably didn't notice when you played Nintendogs or Nintendogs + Cats as an innocent youngster is that, while bathing the animals, they definitely had a very specific and deliberate change in their facial reaction when you would spray some of the more "sensitive" parts of their anatomies.
2 Why Is Mom So Happy Lately?
Here we go, another example of a game featuring Princess Peach and an "accessory" that is typically stored in a drawer in a woman's bedside table. Only in this case, things are not only much more blatant than they were in Super Mario RPG, but the game's ending completely revolves around the "Vibe Scepter"— yes, that's really what it's called— the reason your mom has been so much happier lately.
1 Pokéball Jokes Write Themselves
When your game includes an item called a "Pokéball," it is very difficult not to include jokes that make fun of how naughty-sounding its name is. Sure enough, multiple Pokémon games have slipped in jokes about Pokéballs, including female characters who talk about having to get creative with how to hide them when they are wearing bikinis.
Sources: Nintendo Life, Destructoid, What Culture, IGN, TV Tropes