Also there is probably some level of inflation from the characters being present even if they aren’t necessarily part of the act. IE a porn comic where Bart and Lisa are complaining about thumping, cut to Marge and Homer fucking.

I rather like my hentai and have seen this type of thing frequently enough to say it’s semi common. Though I am not into Simpsons personally, a bit too abstract and too far away from human coloration to enjoy.