In Mad Monster Mansion in the first game, you're flushed down a toilet and there's a room containing piles of literal crap. You have to climb up one of them if you want 100%, much to Gruntilda's disgust.
Grunty: I can't believe you went in there, wash your hands now, filthy bear!
In Banjo-Tooie, there is a chamber where cheat codes are entered. The top line reads "ESRA"; reversed, it spells "ARSE" (and possibly a thinly-veiled poke at the ESRB). Knowing the sense of humour favoured by the game's creators, the British company Rareware, this was probably intentional.
Banjo-Tooie featured a life-draining super-weapon with only two buttons on it — "Suck" and "Blow". And the weapon's name? Big-O-Blaster, abbreviated B.O.B., which also stands for Battery-Operated Boyfriend...
The air plug on the giant inflatable Mr. Patch is located between its legs, though Nuts & Bolts has the plug be on Mr. Patch's chest instead.
The crates in Grunty Industries labelled "Big-O-Pants"note Big O is slang for an orgasm. Nice!
In the first game, one of Grunty's possible secrets that Brentilda tells you is that her party trick is a "scary striptease." How exactly that got past the radar is anyone's guess.
Rather than read the article, you might watch these two (somewhat satirical, though, keep that in mind) videos that do this job for us: here and here.
In the "Tower of Tragedy" segment, the incorrect answers for one particular question are the names "Roger the Cabin Boy" and "Rear Admiral Browneye." (Grabbed by the Ghoulies actually has a character with the former name.) Another question offers incorrect answers "W. Anchor" and "M. Bates." (Two of which are a Shout-Out to the false innuendo accusations leveled at Captain Pugwash.)
Similarly, one of the incorrect character names in Grunty's Furnace Fun is "Browneye The Dirty Pirate".
As well as Kazooie apparently "liking it rough", the entire game is basically the crap in Getting Crap Past the Radar, especially Kazooie.
Jolly's Bar has several instances of this:
The menu: "Seaman's Surprise", "Salty Dumplings", "Toad in the Hole"? Just what sort of establishment is Jolly running anyway?
Behind the bar there is a barrel labeled "Ginger Beer", which, while it is an actual beverage, it's also a British slang term for a gay man. Pretty much everything about Jolly is a gay joke.
One of the incorrect answers to a Jolly Roger question in the Tower of Tragedy is "Cabin Boy's sausage". Err...
Jolly Roger himself comes across as homosexual, what with the way he talks and sways. Just listen to his "voice."
His... partner, Merry Maggie Malpass, who has a rather masculine physique and a deeper voice than he does. And when you rescue "her", she claims that Jolly will "need a little relief".
Jolly will say this exact quote if you hit him with your wrench or run into him with your vehicle in Nuts and Bolts:
"Ooh no. Get off! I don't like the rough stuff!"
Banjo-Kazooie: Nuts & Bolts keeps this trend going:
Mumbo has a coconut farm in Nutty Acre's called "Mumbo's Nuts" and worries that when a bomb explodes, his nuts will be blown sky-high. One of the achievements is called "Shower of Gold", and we all know what a "golden shower" is....
One of Banjo Land's mission titles is "You'll Go Blind, You Clanker." In context, the title makes perfect sense, as the mission involves protecting Clanker's eyes from being assaulted and stolen. But thinking about what Clanker rhymes with...
"Floater in The Pipe." That is all.
Tooie introduces several characters with "Minge" in their names. There's also Klungo's name...
Just to count, there's Mingella, Mingy Jongo, and, of course, the Mingos.
In Grunty's Revenge, Honey B, who is responsible for extending Banjo's life meter, will be happy to "give you an extension!", and Banjo claims: "I can't wait to get my hands on your honeycombs!"
The Game Over cutscene from the first game. (Until Ugly Tooty comes out and turns the situation creepy.)
The Saucer of Peril has "bleep" as a Verbal Tic. When you win both prizes in the Saucer ride in Tooie it tells you you've won two bleeping prizes.
There is one question in the Tower of Tragedy quiz... it's not too explicit, but it certainly merits mention.
What is blocking the vents in Grunty Industries' sewer system? >Squitters >Clinkers >Turdlets
When you win the first Jiggy from Canary Mary in the mines, she says it's been shoved up her wing for a while, which Kazooie finds gross. Not too bad by itself, but it's followed up when you win the Cheato page from the second race when she begins to say where it's been before Kazooie cuts her off. So where was that page, exactly?
In a measurably past-the-radar example, in Tooie, the boss fight against Lord Woo Fak Fak (no, this isn't about his name) has you shooting at his boils, which billow blood into the water. Blood is actually taboo in E-rated games according to ESRB standards, and usually results in an automatic T-rating. Previous games have even had to make changes due to this rule (a notable one is Ocarina of Time, where a Coughing Up Blood scene turned into a Vomit Indiscretion Shot), yet somehow, Tooie got away with it.
Another one from Tower of Tragedy:
What item did the pawnbroker at Jolly Rodgers Lagoon have for sale? >A Jinjo >A Cheato page >A pawn magazine
The bikini girl from the first game's ending carrying two giant, conspicuously placed melons.
Mumbo's chant "Oomenacka" is actually composer Grant Kirkhope complaining about pain in one of his testicles. "Knackers" is British slang for balls, so the phrase is actually "Ooh, me knacker!"
Nintendo made sure to avert this trope at one point. They originally believed that the flower pots outside the chapel said "Fuck you" when you spit eggs into them, when it was really "Thank you" all along. Grant Kirkhope had to redo it several times to get them to believe it was "Thank You."
Of course, plenty of fans still hear "Fuck you".
If you watch the opening of the first game, you'll notice that Kazooie isn't playing a kazoo. She's playing a horn. So, give the Theme Naming, she should be called Hornie. The game should be called Banjo—Hornie.
Even the Idle Animation from the first game pulls this off. Kazooie will start pecking Banjo out of boredom, and the second time she tries, Banjo catches her by the neck and chokes her.