Probability Pileup

The Theory of Narrative Causality aside, there are many things that are NOT probable. Green Rocks and Applied Phlebotinum often shift the scales, but seldom the odds - the odds shift themselves.

To word this better, once a thing has happened, it is much easier for it to be done again.

Similar to a mantra in Discworld; once things have happened, they have a tendency to happen again. The probability of an event increases slowly but steadily, until Rocks Fall, Everyone Dies or it approaches 1.

Compare So Last Season.

Applied to defeating villains, heroes, and attacks, this trope leads to Villain Decay, The Worf Effect, and The Worf Barrage.

Anime and Manga

 * In Dragonball Z, the legendary Super Saiyan transformation was seen as impossible to achieve, yet so powerful and dangerous that it merited the destruction of the Saiyan homeworld and the near-genocide of their race. It took Goku, who was prophesied to get it, amazing emotional and physical stress to achieve it. Ditto for Future!Trunks, Vegeta, and Gohan. Then they discovered that there are levels to the Super Saiyan transformation. Then Chibi!Trunks and Goten, Vegeta and Goku's pre teen children, discovered they could transform at will, just because. And then they discovered that the key to the truly legendary transformation (the one that warranted the genocide in the first place) were the Saiyan tails that Goku and Vegeta had long since gotten removed as liabilities.

Literature

 * In the Discworld novel Monstrous Regiment, the main character is a woman. However, it is gradually revealed that apparently so is everyone else in her squad, with the exception of the nebbishy lieutenant, and including The Trope goes as far as to take Refuge in Audacity.
 * Somewhat justified, however, in that the long-lasting war had slowly exhausted the nations supply of young, healthy men.
 * The Ellimist Chronicles establishes that while the odds against the Ellimist's ascension were tremendous, the odds of it happening a second time, to Crayak, were very good.

Tabletop Games

 * Warhammer 40,000? Just going by its description on this wiki, there can't be anything they could throw in that would seem too ridiculous.
 * The game is kind of based on Up to Eleven, but not really all that unpredictable. The Imperium is inefficient and draconian, Chaos is equal parts insidious and obvious, the Orks fight everything, the Tyranids eat everything, the Necrons kill everything, and the Tau don't know anything. Cegorach planned one gambit the Deceiver planned the opposing one, and Tzeentch somehow planned them both. Above all, the galaxy is an absolute Crapsack World - the real question in the Imperium's struggle against Chaos, the Necrons, and the Tyranids is which one will destroy it first.