The reason the natural gas tanker was chosen to carry animals was never resolved, nor is the damage to Seoul brought up. Stan's peace with religion is only partially resolved by his love with Francine.
The jet directed by Jeff bears the number A113, a recurring gag on the show and in animation.
The same jet makes multiple passes and a landing on the flight deck.
Stan originally washes ashore naked. A wave that follows provides him with a loincloth.
In "Killer Vacation", Steve took an extended amount of time watching Jeff and Hayley make love on the beach on the same pretense of making sure it was them.