Nuke the fridge is a colloquialism used to refer to the moment in a film series that is so incredible that it lessens the excitement of subsequent scenes that rely on more understated action or suspense, and it becomes apparent that a certain installment is not as good as a previous installments, due to ridiculous or low quality storylines, events or characters.
The term comes from the film Indiana Jones and the Kingdom of the Crystal Skull, in which, near the start of the movie, Harrison Ford’s character survives a nuclear detonation by climbing into a kitchen fridge, which is then blown hundreds of feet through the sky whilst the town disintegrates. He then emerges from the fridge with no apparent injury. Later in the movie, the audience is expected to fear for his safety in a normal fistfight.
Fans of the Indiana Jones series found the absurdity of this event in the film to be the best example of the lower quality of this installment in the series, and thus coined the phrase, “nuke the fridge”.
The phrase is also a reference to the phrase “jump the shark”, which has the same meaning, only applied to a television series instead of a film series.