Presumably, this means either Fox's ban on butts has been lifted, or some rogue animator is getting fired for that blunder.
There Was A Penis In Last Night's Simpsons Episode
Whoops!!! It looks like Bart Simpson's carbon rod accidentally made a repeat appearance for a few frames in last night's Simpsons episode, "Specs in the City." An editor on Simpsons Wiki took a screencap to preserve this watershed moment in network television history for future generations. Those frames have yet to be censored or removed from the Hulu version of the episode (in the name of journalistic integrity, this reporter had to redeem his hard-earned Bing rewards points to get a Hulu Plus subscription in order to confirm it wasn't a hoax).