If you want to see something inappropriate involving Sonic, well, you can just type "(Your Name) the Hedgehog" into Google. But if you want something that was made in an official capacity, there are plenty of animated adaptations to choose from.
Many grew up with the Steve Urkel-voiced "Sonic the Hedgehog," which featured this bedtime story scene.
The character reading to Tails is Bunnie Rabbot, a cyborg lagomorph whose personality is entirely comprised of .wav files of Rogue on the X-Men cartoon. This line probably got past the censors because she's a down-home Southern girl with the dialect to prove it, but "one-eyed snake" is slang for penis no matter where you come from.
Flashing forward to the recent Sonic Boom, Eggman got away with this gem.
In the universe of the show, Eggman is talking about cleaning his collectible dog toy. In any other universe, Eggman just told everyone he was stroking his panty snake.
Most of the sneaky lines we've seen so far rely on a squeaky-clean surface-level appearance in order to hide their underhanded obscenities. Japanese TV is a little bolder, as we see with Sonic X.
You can imagine that this line, followed by the shocked expression of the officer (and the chuckles of her co-workers) would be pretty hard to get past US censors. The localization team didn't even try to make sense of it, instead making Rouge the Bat call the officer an "old lady." They probably figure anyone wanting a Sonic character reference bondage already has a DeviantArt account.
Though Warner Bros Animation only granted Freakazoid a handful of episodes, they sure made an impression. The show took its sister program's maniacal characters (more on them later) and compounded them into one off-the-wall superhero. Freakazoid himself is an unfiltered cartoon, resembling a zany splice of Daffy Duck and Roger Rabbit. Even the ol' Uranus joke becomes funny with Freakazoid's delivery.
Though the character is often bouncing off the wall, Freakazoid still shines in his quieter moments. This is probably the most infamous scene from the entire series' run.
It says something that this makes way more sense with the gay subtext than without it.
Slightly lesser-known but even more racy is this line from Guitierrez, played to perfection by Ricardo Montalban.
Once more, the reaction shot is pivotal -- if the character is grossed out at the idea of having his "man juices" wrung from his genitals, the writers are too.
Most cartoons pick a specific angle and build its characters around that theme, whether it's robots or rodents or uh, precious alien stones that manifest holographic forms in the shape of female humans. The Amazing World of Gumball, however, features cats, flowers, clouds and amorphous blue blobs.
This sets up all kinds of weird pairings; in "The Storm," for instance, a balloon and a cactus start dating at the very inclusive middle school where much of the show takes place. Gumball is sickened by the cuteness of the adorably mismatched couple, and intentionally breaks them up.
Later, Gumball apologizes to his friend Alan the balloon, but it seems to be too late -- he's already deflated. Alan claims that he doesn't have the strength to restore his shape, so he asks Gumball for a little help.
Yep, that's a living balloon, in a junior high bathroom, asking his friend to blow him. Judging by the very next shot, Gumball agreed -- but he wasn't happy about it.
As ever, the faces say it all. Alan feels light as a feather, whereas Gumball looks like he'll never be the same again.
How can modern cartoons get away with this stuff? Well, it's all thanks to the precedent set by the Warner Brothers (and the Warner Sister)...