Happened in many Looney Tunes shorts with surprising frequency. Why? Because the animators and writers didn't have to worry (much) about standards and practices boards (besides The Hays Code), the Looney Tunes were meant more for an adult audience (though, unlike modern-day adult cartoons, they didn't latch on to gross-out comedy and raunchy sex to get laughsnote something modern cartoon writers should take note of), and even if they did have to worry about indecent content, The Hays Code officers went after vaguely sexual or subversive content in both live-action and animated movies rather than the stuff that would today be considered plain as the noses on their faces. So, you see, kids: even back then, the censors weren't very bright.
Speedy Gonzales is always singing "La Cucaracha." A Bilingual Bonus in that the cockroach of the title is looking for "marijuana por fumar." To smoke.
The Pepe Le Pew cartoons would qualify (after all, the whole series is a Stealth Pun on men going after pussy...cats), though one Pepe cartoon will make viewers wonder why the Hays Office didn't intervene: 1953's "Wild Over You," in which Pepe's latest feline victim is an escaped wildcat who fights off Pepe by beating him up. The crap that got past the radar is Pepe stating that he liked it.
Another example was not so much as getting past the radar as the radar was about ten moves behind: During one pursuit, Pepe calls out to Penelope: "You are too tightly wound up! You should try engaging in some recreational activity, like making love!" It wasn't quite so risque a term back then as it is now, but it still qualifies given The Hays Code and its rules on sex in cinema (including verbal implications of it).
in "What's Cookin', Doc?", one of the films is a "stag reel" (the old name for a porno movie, particularly one that plays as part of the entertainment at a bachelor party or a guys' night out). Since the films are ones Bugs starred in, the implication is that Bugs was a porn star.
"Hare Conditioned" (Jones, 1945), has Bugs in drag as a female customer in the shoe department trying to fool the store manager (who wants Bugs mounted and stuffed, having served his purpose as a store window prop). What the manager does following this dialogue would be tantamount to sexual harassment today:
Bugs: I'd like to see something nice in a pair of bedroom slippers.
Manager: Confidentially, so would I!
"Hollywood Daffy" (Freleng, 1946) has Daffy impersonating a studio director fooling the o-fay Joe Besser-like gate cop into thinking he'll make him a star. Daffy examines him and asks "What's Errol Flynn got that you haven't got?" before interjecting, "Don't answer that!" So what does Errol Flynn have that the studio cop doesn't? Apparently, a statutory rape charge. Errol Flynn was notorious as a ladies' man and was accused of seducing two teenaged girls a couple of years prior to the cartoon's premiere. Flynn was acquitted of all charges.
"A Gruesome Twosome" (Clampett, 1945) features a pair of alley cats, one a Jimmy Durante-like guy, the other a mostly silent deadpan, both after Tweety. At one point they're disguised in a two-man horse costume. The Durante cat pulls off his headpiece and tells us "I'm the horse's head!", which of course makes the other guy the horse's ass.
In "Bewitched Bunny" (Jones, 1954), after Bugs turns Witch Hazel into a female rabbit, he turns to the camera and remarks, "Ah, sure, I know, but aren't they all witches inside?" That line was actually the subject of controversy in Canada, of all places, for being misogynistic (and yet, America — which has Moral Guardians by the boatload going after every little thing and chipping away at what's supposed to be fun and entertaining, regardless of age — did nothing about it). The case in Canada was dropped after a few days.
In the original theatrical release of "Devil's Feud Cake", when Satan first sees Yosemite Sam, he says to him, "Well, who in Hell are you?".
In "Book Revue" (Clampett, 1946), one of the books is called Cherokee Strip, presumably about the region in Kansas, but the cover has a picture of an Indian girl in revealing clothing accompanied by cheers and wolf whistles.
In "The Draft Horse" (Jones, 1942), they sneaked in the old marching song "You're in the army now" on an eyesight test, which featured the verse "you'll never get rich/you son of a bitch" (written so small it's almost illegible without pausing).
In one Road Runner short, Wile E. Coyote's Canis Latinicus scientific name was given as "Hardheadipus oedipus", i.e. hard-headed motherfucker. Meanwhile, the Road Runner's Canis Latinicus scientific name was given as "Batoutahelius".
A surprising example in a much later Looney Tunes cartoon is in "Bunny and Claude" (Mc Kimson, 1968), where at one point as the Bonnie and Clyde-esque gangster rabbit duo that only steals carrots is trying to evade the sheriff, Bunny says to Claude "I just want to tell you that there's a..." and whispers inaudibly. Claude then turns to her and says "Is that all you ever think about? ...Carrots?"