"Voice command authorization. Be human."
- Ghost, Halo Legends:Prototype
"HAHAHA! You get it?! "Be human"! It's what that girl told him earlier! It represents his development as a character!"
- Random Voice, Prototype Abridged
Alice used to think giraffes were lame. However, soon after embarking on her grand quest she meets a giraffe and the two are forced to work together. Over the duration of her journey, Alice learns to appreciate the long-necked species. During the final battle against Bob the Poacher, Alice is brought down to her knees. When Bob inquires as to why she fights so hard to defend the animals, Alice replies, "Cuz giraffes are pretty damn cool." She then summons some magical giraffe phlebotinum and you can guess where the rest of the story goes from there.
Such a line falls under this trope. Whenever a piece of dialogue represents the completion of a character's development, this trope is at play. It can be as short as a single line of dialogue or it could be an entire speech.
The trope usually occurs during the climax of the story and is commonly found in the Final Speech, the "The Reason You Suck" Speech, the Patrick Stewart Speech and other such climactic dialogue.
It makes a great alternative to the Pre-Asskicking One-Liner.
Since this trope is generally found toward the end of a story, be wary of unmarked spoilers in the examples.