In "The Price," right after Owen dips his hand into the magic cauldron-brew and his hand gets turned to stone, in the last frames of the episode he grips it in a way that is totally flipping Xanatos off, the full arm-gesture equivalent of flipping someone the bird. It's not even subtle. Now, one COULD argue that this was unintentional, since it would likely be completely out-of-character for Owen... but Puck?
It is not used as an expletive (but, all the same, the word isn't allowed on children's television), but Xanatos says in "Awakening, Part Two," "Pay a man enough, and he'll walk barefoot into Hell." The line was edited out when the episode was put into VHS release, but the DVD version has the line uncut and uncensored.
Hyena's decidedly unsubtle machine fetish is not exactly getting past the radar; more like making out with the antenna.
Hyena: Wanna make sparks fly?
Jackal's jealousy comes off as a bit disquieting too.
Hyena(speaking of Coyote): I find him very attractive.
Jackal: Well, that's sicker than usual.
Also, the fight between Elisa and Demona at "High Noon." The exchange between Coldstone and Macbeth as they watch the fight might qualify as a Parental Bonus:
Coldstone:This is... diverting.
Macbeth:You don't know the half of it.
In a flashback scene of Bad Guys, young Dingo flat-out (albeit jokingly) asks John Oldcastle if he is a child molester. But then, the comics are pretty violent as it is.
"Eye of the Beholder" shows an unmarried Fox and Xanatos living under the same roof (In a Disney show, of all places.) Given their previous behavior with each other, you CAN'T think that Xanatos ISN'T tapping that.
Greg Weisman's timeline (and Alex's age in the comics) confirms that Alexander was conceived later on the same night David proposed.
Then in "Vows," the subsequent episode, after the bride-to-be Fox tells Xanatos that she's about to "get changed for tonight," Xanatos watches her leave... with his eyes fixed squarely on her butt. The smirk on his face makes his inner thoughts quite readable.
In the first story of Gargoyles, Goliath asks to be turned to stone with the same spell that the Magus cast on his surviving clan. Since the escape clause of the spell is the seemingly impossible "Until the castle rises above the clouds", what he is requesting is basically assisted suicide. The fact that the story jumps ahead 1000 years to see David Xanatos fulfill that condition and release them hides that fact.
There's the infamous "Kinky" line uttered by Fang upon watching Demona change from gargoyle to human. Greg Weisman himself admitted he wasn't sure how they got that one past the censors. Eventually, the censors did notice and it did get removed from reruns.
In "The Mirror," after Puck has turned all the humans in the city into Gargoyles, Lexington, Brooklyn, and Broadway look on in shock at what has happened, while doing so, a group of female Gargoyles wearing little clothing and their wings covering themselves walk by and smile at them rather flirtatiously. Judging by their expressions, no doubt all three boys are thinking of one thing and one thing only right now.
Two of them, anyway. The other is busy summing up the situation as "kinda fun... but weird."