7. The Island
Also, the bizarre ending of "The Computer Wore Menace Shoes" leaves the Simpson family trapped on a mysterious, LOST-like island in a state of drugged stupefaction due to constant mysterious gas attacks from random unexpected objects including family dog Santa's Little Helper, in a thorough parody/homage of the British cult 60's series The Prisoner. This unresolved cliffhanger was never mentioned again by the series, which leads inevitably to the outlandish but just as plausible as everything else theory that the entirety of events since this point on the series has been in fact nothing more than a mere gas-induced hallucination. You can't disprove it, can you? Well, there you go.