Plotkai 

Main or sub characters that gain extraordinary power for no absolute reason other then to surpass their current situation due a lack in power. These characters, will be as strong, as they need to be.

Ash's Pikachu is able to beat legendary pokemons with no real extensive training.

Ichigo is part Hallow, Shinigami, Human, and Quincy. Also has the ability to use Bankai, Full bringing, Instant Regeneration, Hallow Form, Hallow 2nd Form.

Sasuke and Naruto for some reason are stronger then Hokage's and can match the Sage of 6 Paths.

All three examples are forms of Plotkai, where they protagonists will be as strong as the plot requires.

Plotkai by SimplyPresent May 12, 2014

Plotkai 

Plotkai means a way for an event happening without explaing itself, like why it happend, and what triggered it. (Mostly used in Anime and Manga series, when a character gains an unexpected powerboost or new abbility just so he can defeat someone stronger than him/her.) These events will be left unexplained nearly allways, for there is no logical explanation for them, exept Plotkai, which means the actual event had to happen to keep the continuity of the story's plot, hence the name: Plot-kai.

Ichigo being able to cut, then defeat Kenpachi is Plotkai, since no other characters have been able to do this, including the ones much stronger than Ichi. He was able to do it because hes the main hero. Thats plotkai. (reference: Bleach)

Plotkai by Kenchan July 25, 2007

Plotkai 

A mix of the words "Plot" and "bankai". Refers to a plot twist in the manga series Bleach where the main antagonist (Aizen) appears defeated, only to be revealed that he used hypnosis to switch himself and Momo, injuring her instead.

Whoa! All that time they were beating the crap out of Momo instead of Aizen? Major Plotkai!

Plotkai by MyToesAreCold July 31, 2010