Well that's ridiculous, I don't know if you're intentionally being sandy vagina'd after what I wrote before, but you are taking the notion of it being "believable" as in "Do I actually think a yellow cartoon family live in a place called Springfield?".
Even in sci-fi and folklore, whatever, there are stories that involve logic and rhythm that you "believe" as in, within that universe, you connect with the ideas that under these circumstances, regardless of how different they are to our own reality, it still makes sense. The logic of the characters, the sequence of events, this is all "believable" within the confines of
that reality.
When Bart ends up working for the mob because he had to get an after-school job (one of the best episodes ever) it all made sense, the way things fell into place, his reasoning for being around the mob, the reasoning for the mobsters to see something in this kid they like, it all worked perfectly. From there they could be absurd, they set a solid base and tone, they could then make the mobsters silly, like real people but goofy, and that worked because of the believable context.
However, and this is going from memory from an episode I hated over 10 years ago, when Bart decides to legally emancipate himself from his father over something absolutely stupid (it was a really poorly constructed "argument" about how he couldn't leave the house or something ridiculous) and ends up living in an attic above a skating arena owned by Tony Hawk, then that is not a believable context, and not only were attempts at absurdist humour sh*t anyway, but the context ruined any chance of even wanting that episode to be funny.
So that's 2 examples of episodes then, and episodes "now" (they've been the same level of shittyness for the last 15 years so "now" is the same as 10 years ago). One is a believable context and a well thought out storyline where everything correlated, the other was a ridiculous reason to plug a guest celebrity, just for the sake of it.
