It's a me! Mario-o...oh...oh, mama-mia.Super Mario RPG: Legend of the Seven Stars
This game has a variant of the classic Mario villains, "Shy Guys." These versions are known as "Shysters." It's also a word describing an unscrupulous person (particularly lawyers) that has tended to carry an anti-Semitic connotation.
Yaridovich claims, "I got to my lofty station in life by... ahem... 'pleasing' my superiors."
Valentina's 'hit' animation seems to involve little but gainaxing.
If you look around her bedroom, you can find Princess Toadstool's "???". We're not told what it is, but her grandmother will immediately run over and bribe you to leave it be. Go back and find it again when the princess is in your party, and she will yell at you for going through her things. The original Japanese name is "Peach's XXX", but in Japan, "XXX" is typically used in the "insert word here" sense, making it have the same meaning as ???.
Many fanartists have jumped on this odd lack of description, usually interpreting it as being underwear of some sort. Except when they decide it's something else a lady might keep hidden in her bedroom.
One of King Calimari's (a gigantic octopus, for the record) attacks is to use one of its tentacles to snatch away one of your party members. When they're returned to the battle a few turns later, they'll have gained the "Fear" status. Hmm...
One quest involves returning a "special tape" from Goompa in Goomba Village to Koopa Koot in Koopa Village. The contents of the tape are never mentioned, save that Goompa keeps it... well hidden.
During the scene where Peach can disguise herself as one of Bowser's troops, you can interact with a particularly flustered Hammer Bro in the library. He protests that he's not looking for "that book", and bribes you to leave.
Paper Mario: The Thousand-Year Door
Similar to the tape from the first Paper Mario, this time with a mysterious 'package', from one Goomba to another. Add to this the fact that this delivery is made in the back streets of Rogueport, and the Goomba for whom you're delivering it tells you not to be seen, well, it just speaks for itself really. This happens in the third game as well.
A very easily missed "crap past the radar moment" is when Mario is trapped in the cage by Crump in Chapter 2 with all the Punis. Use Goombella on Puniper [the big Puni] and she'll say, "That's Puniper of the Punies. He's a little bigger than the others, obviously. So maybe he can help us reach that special area... Hee hee! Just kidding. His only special power is complaining, I think." 'Special area' would not be that suspect if she hadn't immediately said, "Just kidding." This tattle, by the way, only occurs when you are in the cage — after you get out of the cage and free the Punis, you'll get a different tattle.
Also radar-dodging is one of Kammy Koopa's lines after her visit to the Glitz Pit, regarding shaking what her momma gave her — in wavy text to emphasise it.
The between-chapter Peach segments contain a few instances of Fanservice that managed to scoot by the radar. Some chapters allow you to have Peach take a shower before meeting with TEC (the first chapter requires it) and one chapter has Peach pull an Invisible Streaker to sneak around the enemy base. Nothing is shown on screen, mind you, but even the implication of nudity is surprising for a Mario game.
Super Mario Sunshine
When Bowser Jr. claims Peach to be his mother, Peach has to think about it first before saying she isn't.
Throughout the game, Peach is fighting for control over the Vibe Scepter. Yes. You read that right — a scepter with a vibe. And it's not just the name that's suggestive, the shape of the thing wouldn't seem too far out of place on your average adult-novelty-toy site, either.
To make things worse, here's the on-screen text describing the Vibe Scepter at the end of the game: "The Vibe Scepter has strange and mysterious powers, that's for sure... Maybe... Just maybe... The Vibe Scepter is hidden away in your house somewhere... Your mom's been laughing happily a lot? One thing about that scepter: no one knows who created it or why, but... Somewhere, someone might possibly be using it right now...... What?"
In Mario & Luigi: Partners In Time, Toadsworth repeatedly, in every line of the tutorial, insists that the Bros. Ball move (in which both brothers interlock their bodies to form a ball) "requires a bit of an open mind", that it "is not a bit odd" and that the audience should "keep the jokes to themselves", amongst other things about how innocent it is.
In the French version of Bowser's Inside Story, one area is called "Cul de Sac". Now, Cul de Sac is a perfectly acceptable term, but said area is inside Bowser's... rear area (And "Cul" is basically French for "ass"). That's right: the translators managed to say "Ass" in a Mario game.
Building on Bowser's Inside Story, Fawful literally yanks Peach out of Bowser's ass (thankfully via magic rather than more direct means). Bowser's response? "Hey, put that back!"
There are countless mini-games that, thanks to the camera angle, have you staring directly up Peach's or Daisy's dress. Slightly mitigated by the fact that getting such a view reveals them to have nothing but void above the knees.