Throw It In

Strong Sad: And this part here represents Rondell's transformation into a new man.
Homestar Runner: I thought you said that was just an accident that happened because you loaded the film wrong.
—Homestar Runner, during an audio commentary for a music video of "Experimental Film", performed by They Might Be Giants

The preservation of ad libs, improvisations, and the occasional accident or mistimed what-have-you for dramatic or comic effect, sometimes at the cost of continuity.

These are often some of the most memorable scenes, for better or for worse, due to their spontaneity.

Differs slightly from attaching Hilarious Outtakes to the ends of shows. Related to No Fourth Wall. See also Rule of Funny, Rule of Cool.

Not to be confused with Enforced Method Acting, when something unexpected is deliberately done to an actor in order to elicit a realistic response, or Improv, where there is very little or no script at all and the actors are making up large chunks as they go along.

Compare:

Ascended Fanon: Where Fanon becomes Canon
Ascended Meme: Where a meme from fanon is upgraded to canon.
Ascended Glitch: Like Thrown It In, but occurs after the release of the work.
Harpo Does Something Funny: Invoking this by leaving gaps in the script for the actors to throw stuff in.
Left It In: When it's explicitly said on camera that something will be cut from the final product... and it's not.
Official Fan-Submitted Content: Asking fans for stuff to throw in.

Contrast Blooper.