Julien: I do not intend to fail. I intend to do the opposite of fail!
Marlene: You mean...succeed?
Julien: No, I will not suck seed. No one will be sucking seed!
In "Jiggles", King Julien grabs the pineapple-scented suntan spray and sprays his face, his armpits, his sides, his booty and tail and then... two more times where we can't see but can hear. Then he looks at the penguins and asks, "What, too much?"
"A Christmas Caper" had a scene that involved chugging eggnog from a beer-bong-style funnel.
And in "Plush and Cover", Julien gets rather risque with his requests to be "woken up" by Maurice, including being spanked. But only on the right buttock.
In "Needle Point," Skipper reassures the other three penguins during their checkup by saying: "Turn and cough boys, turn and cough."
Also in "Needle Point," Phil makes some unseen sign language, to which Mason responds, "You groom your mother with those hands?"
At the end of "Field Tripped", Mort rather assertively takes Julien's 'booty scratcher' and uses it to scratch his butt himself. Julien's reaction to this could only be described as "orgasmic". He has a less obvious but similar reaction in "The Officer X Factor": after many attempts by the lemurs at rain-dancing during a heatwave, it coincidentally starts raining just as Mort accidentally kicks Julien's behind. Julien assumes this is what set it off and demands Mort kick him again, sounding rather too enthusiastic as Mort continues. (Possibly the rain was caused less by the penguins accidentally seeding the clouds with salt and more by a Sky Spirit Yaoi Fangirl?)
The hoover dam(n), and the shi(i)t-ake mushrooms.
There was one episode where Skipper didn't even opt for the pun on "Dam," and just used it outright as an exclamation.
"Hello Dollface" reveals the name of the toyline Rico's doll comes from: Ms. Perky.
When Julien sees Rico passing by with his doll, he starts hitting on her... and casually confirms he was flirting with her, not Rico. Which, after "Kaboom and Kabust"...
Rico turns hippie, much to Skipper's horror, and when invited to go blow something up he says, "Uh-uh. Make love, baby." They get away with it because of Rico's mangled voice making it slightly harder to tell what he's saying.
In "The Big Squeeze," Julien remarks how glad he is that he isn't a mammal when all the other small mammals start disappearing. Kowalski helpfully verifies his warm-blooded nature in a rather intrusive way. The expression on Julien's face is pricelessly funny.
In the episode "It's About Time", Skipper and Private are rolling around on the floor fighting over a flask of Macguffium-2000, and Julien and Maurice spot them.
Julien: (bashfully poking Maurice's chest) Look at them Maurice. Why can't we play affectionately like that?
In "Paternal Egg-Stinct", Kowalski looks under Julien's tail while asking him if he's part platypus, as Julien believes that an egg found in Marlene's habitat will hatch into a baby lemur. Later on in the same episode, this exchange occurs:
Maurice: Maybe you should let it go. I'm no expert, but I'm pretty sure whatever is in that egg, it ain't one of us.
Julien: Oh really, Mister Smarty-Booty? And where do you think J.J. will hatch from, if not from an egg? (sips his drink)
Maurice: Well, mammals usually come from...(whispers in Julien's ear)
Julien:(spit take) Do not gross me out with nonsense, Maurice!
Alice mentions that the penguin habitat contains three males and one female. Cue Rico checking his nether regions.
Julien: Mort, take care of these booby traps.
Mort: Booby sounds fun!
At the beginning of "In the Line of Doody," security men are scanning the animals. One sticks his hand into Joey's pouch and Joey replies, "Oi! Out of me personals!"
The entirety of "Kaboom and Kabust," which gives us such things as Julien saying, "You know, I could think of a many other things that could use a good... kabooming... if you know what I mean." Also, the way Rico gleefully shudders at Julien's encouraging him.
When Mort's too entertained by his "Friend-In-A-Box" to fuss over Julien's feet, Julien starts looking for somebody else to do so, starting with Maurice:
Julien: Have you ever noticed my... southern extremities?
Maurice: (horrified/dismayed expression)
In "Love Hurts" Private gets offered some magazines by Kowalski. They fold out sideways, and Private drools when viewing. It's the Lunacorn and Quilting Monthly.
One of Skipper's aliases is an "international playbird."
Any time Kowalski covers Private's eyes is probably an instance of this. He's done this during Marlene's drooling glee over candy, when Mort scratches Julien's behind, and when explaining the complex mating rituals of the Red Rhodesian Slasher (which may be a case of this in itself, if the writers know anything about fandom slang).
The way Marlene comes onto Julien in "Otter Gone Wild" is... very disturbing, to say the least.
Skipper's advice to Leonard in "Kanga Management":
Skipper: Just keep going, and don't stop, no matter how disturbing that sounds!
Maurice, upon being spit up by Savio the boa:
"Tell me we came out of the mouth."
"Operation Break-Spear" has Kowalski attempt to use the lemur's sound-based tactics against them by blaring their own stereo. His Weapon of Choice? Penguin mating calls. Which have no effect on the lemurs, but cause Rico to make eyes and come onto him.
Rico: How you doin'?
Possible Stealth Pun: Jiggles, the gelatinous cube, likes fruit. It then eats Julien.
In "Needle Point" the spellcheck machine is used several times, as is three times repetition. But the 'crap' part comes differently...
Kowalski: If we don't find an answer soo, Skipper may leave the zoo grounds... forever!
(Rico holds up spell-and-speak machine) EVACUATE.
So, uh... think about the many meanings of 'evacuate' for a second or two...
"Mental Hen" has Kowalski seduce a chicken via a mating dance. Said mating dance includes the phrase "Salty Licker, Sister", some... interesting dance moves. and involves him slapping his tail feathers and saying "tell it to the swagger end, baby." And RICO covered Private's eyes at the end of the episode when the Hen kissed Kowalski. Either the censors had just let Tarlok's murder/suicide pass or they had one HECK of a censor Decoy.
In "The Terror of Madagascar" after Burt gets stuck in the wall, Julien leaves in a huff, lifting Burt's tail and...appearing on the other side from Burt's mouth. It's pretty obvious that the censors are dead.
In "Tangled In The Web" we get a closeup of Alice's butt when she spanks it while singing into a banana.