For me it was Series 14, The pop-culture gags and utter lack of original plot devices just sucked all the fun out of it. Now it's just a merchandise machine getting as much product placement in there as possible.

What happened to just coming up with an original story with great, funny, original characters that we could relate to and were developed well? Like the episode Lisa has to go to the boy's side of the school to get a mental challenge? Or the first time Sideshow Bob comes back to murder Bart? It was a big thing when it happened, but now he appears out of nowhere every 3 episodes. It's become too much like Family Guy, a show which I fucking hate the majority of the episodes, with boring, senseless cut-away gags and pop culture references that are out of date and mind-numbing.

(That said, Family Guy has it's moments. The one where Peter drinks all the Red Bull and starts hallucinating had me bad laughing).

what the hell dude