There is an entire episode of exter's Laboratory that was banned from being aired on Cartoon Network. I know this sounds like the beginning of one of those "lost episode Creepypastas" but unlike every Creepypasta lost episode, this actually exists, and can in fact be viewed today.
In the episode titled "Rude Removal" Dexter has invented a machine that will remove all of Dee Dee's rude tendencies. Of course Dee Dee manages to screw up Dexter's plans, although this time instead of blowing his experiment to smithereens, she and Dexter get into a tussle and both end up in the machine. The machine malfunctions and actually creates clones of the two. These clones have all of their rude tendencies.
What follows is a highly funny, highly inappropriate episode filled with censored swearing throughout. Heck the title card features Dexter mooning viewers and Dee Dee flipping the bird.
The actual title card for "Rude Removal"
The episode was shown at various conventions for some time. Finally in January of 2013, after enormous demand, Adult Swim (the late night block on Cartoon Network featuring shows aimed at, what else, adults) aired the episode and uploaded it to YouTube. The segment can be seen below. The swearing is bleeped out, but I would still recommend viewer discretion.